Highly sensitive ITO/GeSiхOу/n-Si MIS photodiode with wide spectral range

Highly sensitive ITO/GeSiхOу/n-Si MIS photodiode with wide spectral range | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Highly sensitive ITO/GeSiхOу/n-Si MIS photodiode with wide spectral range Ghaithaa Hamoud, Gennadiy Kamaev, Michel Vergnat, Vladimir Volodin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9209454/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, we present a highly sensitive photodiode based on an ITO/GeSi х O у /n-Si structure without a p-n junction. The GeSi х O у dielectric layer plays a key role in reducing the dark current by four orders of magnitude compared to ITO/n-Si structures containing only native Si oxide, while the photocurrent decreases only slightly. High responsivity and specific detectivity covering the UV to IR range have been achieved, enabling this structure to be used for detecting optical signals over a wide spectral range. Figures Figure 1 Figure 2 Figure 3 Introduction Modern digital electronics is based on metal-insulator-semiconductor (MIS) structures, which are also widely used in optoelectronics, such as Charge-Coupled Devices (CCDs) and Complementary Metal-Oxide-Semiconductor (CMOS) sensor cameras. Highly sensitive photodetectors (single and matrix) are also fabricated using p-n junctions. However, for over 50 years, efforts have continued to create highly sensitive photodetectors based on MIS structures with tunnel-thin dielectrics [ 1 – 4 ]. The main challenge in developing highly sensitive MIS Schottky barrier photodiodes is to control and reduce the dark current without reducing the photocurrent. Tunnel-thin dielectrics with precisely controlled thickness are used for this purpose. Recently, MIS photodiodes based on a thin silicon dioxide layer (4 nm) have been fabricated with ultra-low dark current and a wide photodetection range from 265 to 2200 nm [ 5 ]. The use of a bilayer dielectric opens the possibility of extending the photosensitivity range to short-wavelength UV. Solar-blind photodetectors based on MIS structures using silicon oxide and germanium oxide have been created; silicon oxide helped to reduce the dark current, and germanium oxide served as a photosensitive layer [ 6 ]. To expand the spectral range, Ge and Si quantum dots [7; 8; 9], and silicon quantum nanolayers were introduced into the SiO 2 matrix [10;11]. An alternative to tunnel-thin dielectrics are non-stoichiometric dielectrics, which exhibit other mechanisms of electron transport (not only sub-barrier tunneling), for example, SiO x , which is used in perspective memory elements - memristors, as well as in photomemristors [1; 13]. Recently, interest has arisen in non-stoichiometric germanium oxide GeO x , in which the memristor effect has also been discovered [ 14 ]. A mixture of silicon and germanium oxides in the form of non-stoichiometric germanosilicate glasses (GeSi x O y ) allows one to vary the transport properties by changing the stoichiometric parameters x and y . Memristors and photomemristors have been fabricated from GeSi x O y [15; 16]. In our previous studies, we demonstrated the photosensitivity of GeSi x O y -based MIS structures [ 15 – 17 ]. In this study, we developed for the first time an ITO/GeSi x O y /n-Si-based MIS photodiode with high specific detectivity in the UV, visible, and near-IR ranges, comparable to that of silicon p-n junction photodiodes. Experimental part In this work, thin GeSi x O y films were obtained by electron beam physical vapor deposition (EB-PVD) under high vacuum conditions. The targets (GeO₂ and SiO₂ powders) were co-evaporated simultaneously using electron beams. The initial pressure in the chamber was (10⁻⁹–10⁻⁸) Torr, but during the evaporation of the targets it increased to 10⁻⁷–10⁻⁶ Torr. The evaporated material was deposited on two types of substrates: the first was n-type Si CZ (100) (phosphorus-doped), with a specific resistivity ρ in the range 6 to 8 Ohm·cm; the second was p-type Si CZ (100) (boron-doped), with a resistivity ρ in the range 10 to12 Ohm·cm. Before being placed in the vacuum chamber, the native oxide layer was removed from the Si substrates by hydrofluoric acid etching. However, the substrates were kept in air for one to two hours, allowing the formation of a "fresh" layer of native oxide. Evaporated components from two targets (GeO₂ and SiO₂ powders) were deposited on the substrate, such that the composition of the deposited film was [GeO v ] z [SiO 2 ] 1−z , where the z parameter was set by controlling the evaporation rate of each target. It should be noted that during the evaporation of GeO 2 powders, due to the different volatility of the Ge, GeO, O 2 , and GeO 2 components, a film of the composition GeO 1.1÷1.2 is deposited [ 18 ]. A quartz microbalance sensor above each source was used to control the deposition rate, which enabled the determination of the evaporation regime for the deposition of a film with the composition [GeO v ] 0.75 [SiO 2 ] 0.25 . Films of this composition were deposited onto n- and p-Si substrates by a unique "side-by-side" deposition process. The thickness, structural properties, and composition of this sample were previously determined using spectral ellipsometry, Fourier Transform Infrared (FTIR) spectroscopy, Raman scattering (RS) spectroscopy, and X-ray photoelectron spectroscopy (XPS), as described in detail in [ 19 ]. According to ellipsometry data, the thickness of the native silicon oxide layer was 2.5 nm, and the thickness of the [GeO v ] 0.75 [SiO 2 ] 0.25 film was 104 nm. RS spectroscopy data indicate that the film does not contain clusters of amorphous or crystalline germanium [ 19 ]. An analysis of the FTIR-absorption results showed that the film contains the following chemical bonds: Ge-O, Si-O, Si-O-Ge. According to XPS data, the z parameter in the [GeO v ] z [SiO 2 ] 1−z film was 0.74, and the film contained 11at.% silicon, 53at.% oxygen, 4at.% carbon, and 32at.% germanium [ 19 ]. Thus, the parameter ν is in the range1.1-1.2. To study the influence of the [GeO v ] 0.75 [SiO 2 ] 0.25 layer on the photosensitive properties of the MIS structure, reference samples were fabricated without this layer, but only with a thin layer of native oxide (Fig. S1a, b). For electrical measurements, top contacts of indium tin oxide (ITO) with a thickness of 150 to 200 nm and a sheet resistance of 40 to 80 Ohm/□ were deposited on the samples by magnetron sputtering through a mask. The size of the contact pads was 0.7 by 0.7 mm. Ohmic contact with the back side of the silicon substrate was achieved by rubbing it with an indium-gallium (In-Ga) paste. The structure was then placed on a copper plate. During the experiments, this side was at zero potential, while a positive or negative bias was applied to the top ITO electrode. A schematic diagram of the MIS structures for all samples is shown in Figs. 1 a–d. The spectral dependencies of the photosensitivity were studied using a monochromator (Nanotechnology Center, Novosibirsk, Russia) in the wavelength range of 400 to 1100 nm (spectral resolution of 8 nm). A halogen lamp was used as the radiation source. To suppress the influence of second-order diffraction radiation during measurements in the wavelength range above 580 nm, a special edge filter was used. Two illumination regimes were applied to the samples. Regime 1: the monochromator was set to the zero-diffraction order (thus, the whole spectrum of the halogen lamp reached the sample), the total power reaching the contact pad was 500 µW, which corresponds to a fluence of 1 kW/m². Regime 2: the monochromator was set to the first order of diffraction (the sample was illuminated by quasi-monochromatic light); at the maximum spectral power, the fluence was 1.6 W/m². In the UV region, measurements were carried out using a 368 nm Light Emitting Diode (PK2B-3LLE-GNVS, 200 mW peak power) and a narrow-bandpass filter that suppresses visible light. Results and discussion Figures 1 a and 1 b show the current-voltage characteristics (I-V characteristics) in the voltage range of ± 5 V for MIS structures without a [GeO v ] 0.75 [SiO 2 ] 0.25 layer on p- and n-type substrates (samples S1p and S1n, respectively) in the dark (black curve) and under illumination by a halogen lamp in regime 1 (red curve). It can be seen that for sample S1p under reverse bias (+ 5 V), the photocurrent is 8.6 times greater than the dark current, and the dark I-V characteristic demonstrates a diode behavior (Fig. 1 a). For the sample on the n-type substrate (S1n) under reverse bias (-5 V), the leakage current is high, so the dark current is almost equal to the photocurrent (Fig. 1 b). The I-V characteristics in the dark of the samples with the [GeO v ] 0.75 [SiO 2 ] 0.25 layer on p- and n-type substrates (samples S2p and S2n, respectively), shown in Figs. 1 c and 1 d, exhibit diode characteristics. Reverse bias (creating a depletion space charge region (SCR) in the semiconductor substrate) is positive for p-Si and negative for n-Si [ 17 ]. For the dark I–V characteristic of the S2p sample (Fig. 1 c), one can see that the minimum current does not correspond to zero bias voltage, probably due to the presence of a built-in charge either in the [GeO v ] 0.75 [SiO 2 ] 0.25 layer or at its interfaces. The main result of adding the [GeO v ] 0.75 [SiO 2 ] 0.25 layer is a significant decrease in the dark current under reverse bias. Thus, for p-Si structures under reverse bias (+ 5 V), the dark current decreases by two orders of magnitude (Figs. 1 a and 1 c), and for n-Si structures under reverse bias (-5 V), the dark current decreases by four orders of magnitude (Figs. 1 b and 1 d). Moreover, for structures on p-Si with reverse bias (+ 5 V), the photocurrent decreases by only a factor of six (Figs. 1 a and 1 c), and for structures on n-Si with reverse bias (-5 V), the photocurrent decreased by only a factor of 3.5 (Figs. 1 b and 1 d). Since the S2n sample demonstrated the best ratio of photocurrent to dark current, its photoelectric characteristics were further investigated in more details. Figure 2 shows the dependence of its responsivity on voltage under illumination regime 1. Using the methodology described at https://www.hamamatsu.com/eu/en/product/optical-sensors/photodiodes.html , the external quantum efficiency can be calculated from the responsivity. The spectral maximum of the halogen lamp's radiation power occurs at a wavelength of 650 nm (photon energy of 1.9 eV). For photons of this energy, with an external quantum efficiency of 100% (i.e., one incident photon generates one electron-hole pair), the responsivity is 0.5 A/Watt. Figure 2 shows that for the S2n sample, at a reverse bias greater than 2.2 V, the external quantum efficiency exceeds 100%, i.e., a photocurrent multiplication occurs. The mechanism of photocurrent multiplication could be either the avalanche effect [ 20 ], or the effect of inhomogeneities in the dielectric, for example, "paths" in the native oxide layer [ 21 ]. Figure 2 also shows an increase in responsivity with increasing reverse bias with two plateaus. The maximum responsivity is observed in the reverse bias range from − 8.5 to -10 V, while (Fig. 1 d) the dark current remains almost unchanged. Therefore, a bias of -10 V was chosen for investigating the spectral characteristics of the photosensitivity. Figure 3 a shows the responsivity dependence on wavelength in the range from UV to IR for the S2n sample at a reverse bias of -10 V, illumination regime 2. The maximum responsivity was observed in the wavelength range of 700 and 750 nm, with its value exceeding the data obtained in references [ 5 – 11 ]. Moreover, this value significantly exceeds the result obtained in a previous work using a dielectric film (GeSi x O y ) of different composition and containing a thin germanium layer [ 17 ]. It is also worth noting that, in illumination regime 2, the responsivity values in the wavelength range from 400 to 1050 nm exceed those obtained with illumination in regime 1 (Fig. 2 ). This indicates a nonlinear dependence of the photocurrent on the fluence, since, in regime 1, it is three orders of magnitude greater than in regime 2. The mechanism of photocurrent generation has been discussed earlier [ 17 ]. For photons in the visible and near-IR ranges, it involves absorption in the depletion SCR of the silicon substrate. However, in Fig. 3 a, a local responsivity peak appears at a wavelength of 450 nm. This peak can be explained by light absorption associated with defects in the GeSi x O y dielectric layer, in particular with oxygen vacancies. These defects create local energy levels in the band gap, which leads to the appearance of a photoluminescence peak in this spectral region and facilitates the generation of photocarriers even with a low absorption coefficient [ 22 ]. We estimate that the dominant noise in the dark current is shot noise, since the fluctuation of the dark current caused by thermal noise at a reverse bias of -10 V, even at high frequencies (1 MHz), is very small (2.47·10 − 17 A). Walter Schottky defined the value of shot noise as the root-mean-square variance of current \(\:{I}_{Shot}^{2}=2eI\:{\Delta\:}f\) [ 23 ], where \(\:{\Delta\:}f\) is the bandwidth, e –is the electron charge, and \(\:I\) is the current value. In our case, the following expression was used to calculate the specific detectivity: \(\:{D}^{*}=\frac{{S}_{I}\sqrt{A\bullet\:{\Delta\:}f}}{\sqrt{2\text{e}{I}_{dark}\:{\Delta\:}\text{f}\:}}=\frac{{S}_{I}\sqrt{A}}{\sqrt{2\text{e}{I}_{dark}\:}}\) [24; 25], where S I is the current responsivity and A is the ITO contact area. The specific detectivity \(\:{D}^{*}\) is measured in Jones [ 26 ]. Figure 3 b shows the wavelength dependence of the specific detectivity of the S2n sample at -10 V. All values over a wide spectral range (from 368 nm to 1100 nm) exceed 10¹² Jones, with the highest value observed at a wavelength of 750 nm (7·10 12 Jones). All these values significantly exceed the data for MIS photodiodes obtained in previous works, which used SiO x with various inclusions [5-11; 19; 25; 27]. The obtained high specific detectivity values are mainly due to the strong suppression of the dark current when adding the [GeO v ] 0.75 [SiO 2 ] 0.25 layer (by four orders of magnitude for n-Si). As shown by the “ ab-initio ” calculation of the band offset in the Ge/GeO x system [ 28 ], the barrier for holes (2.8–3.7 eV) in this system is much higher than the barrier for electrons (0.4–1.1 eV), depending on x . The band offset between Ge and Si is not large, approximately 0.4 eV for holes (for epitaxial heterostructure). Therefore, the barrier for holes in the Si/GeO x system is also much higher than the barrier for electrons. Under reverse bias in n-type silicon, electrons move against the electric field, i.e., toward the bottom contact, while holes should move toward the top contact, but they are minority carriers, and their transport is suppressed due to the high barrier in the dielectric. As a result, the dark current is suppressed. Under illumination, the depletion SCR depth decreases [ 19 ], reducing the voltage drop across the substrate. However, the voltage drop across the dielectric layer increases, increasing the electron component of the current, i.e. the contribution of electrons injected from the top ITO contact. This compensates for the decrease in hole current, so that the photocurrent decreases by a factor of only a factor of 3.5 compared to the structure without a germanosilicate glass layer – S1n. Conclusion In conclusion, the MIS photodiode based on non-stoichiometric germanosilicate glass has been fabricated, and its spectral photosensitivity has been studied over a wide spectral range. Experiments demonstrate its high sensitivity and responsivity, as well as its relatively low dark current, enabling a specific detectivity up to 7·10¹² Jones. The introduction of a non-stoichiometric germanosilicate glass layer into the MIS structure opens the way to the development of low-cost, highly sensitive photodetectors without the need for p-n junctions. Declarations Competing Interests The authors have no relevant financial or non-financial interests to disclose. Funding This work was supported by the Ministry of Science and Higher Education of the Russian Federation under Project No. FSUS-2024-0020. Additional funding was provided through the state assignment (theme No. FWGW-2025-0023). Author Contribution G.A. Hamoud contributed toward conceptualization (equal); data curation (lead); formal analysis (equal); investigation (equal); writing – original draft (equal); writing – review & editing (equal). G. N. Kamaev contributed toward conceptualization (equal); data curation (supporting); formal analysis (equal); investigation (equal); writing – original draft (supporting); writing –review & editing (supporting). M. Vergnat contributed toward investigation (equal); writing – review& editing (equal). V. A. Volodin contributed toward conceptualization (lead); data curation (equal); formal analysis (equal); funding acquisition (lead); investigation (equal); project administration (equal); supervision (lead); writing – original draft (lead); writing – review & editing (lead). Acknowledgement The authors acknowledge the Shared Research Center “VTAN” of Novosibirsk State University. Data Availability Data will be made available on request. References B.L. Sharma, Metal-Semiconductor Schottky Barrier Junctions and Their Applications (Springer Science & Business Media, 2013) A.Y. Vul’, A.T. Dideikin, Photodetectors based on metal-tunnel insulator-semiconductor structures. Sens. 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Hernández Simón et al., MIS-Like Structures with Silicon-Rich Oxide Films Obtained by HFCVD: Their Response as Photodetectors. Sensors. 22 (10), 3904 (2022) R.C. Jones, Performance of Detectors for Visible and Infrared Radiation. Adv. Electron. Electron. Phys. 5 (0065–2539), 1–96 (1953) Z. Huang, Y. Mao, G. Lin et al., Low dark current broadband 360–1650 nm ITO/Ag/n-Si Schottky photodetector. Opt. Express. 26 , 5827 (2018) J.F. Binder, P. Broqvist, A. Pasquarello, Electron trapping in sub-stoichiometric germanium oxide. Appl. Phys. Lett. 97 (9), (2010) Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9209454","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":614890856,"identity":"bd1837b6-2863-40e4-b7ac-ded4a2b903c6","order_by":0,"name":"Ghaithaa Hamoud","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYBACCRCRAMT8pGuRbCBJCwgYHCBWi2QD+8UPD/7YyRufX8D28GcbQz5BvdIMPMUSiW3JhttuPGA35m1jsNxASIscA0+CRGIDM+O2GwfYpBnbGAwI2gLUkvwj4U+9/eYZB9gkfxKjRZqB/ZhEAtvhxA38DWwSvMRokWzmYbNIbDuePOMGY5s0zzkJA0lCWiSOtz+++eNPtW1//+Fjkj/KbAz4CGlhYOYxgGpObGBAiid8gP0BhOYnaPooGAWjYBSMVAAAfWw8kvnbTHMAAAAASUVORK5CYII=","orcid":"","institution":"Novosibirsk State University","correspondingAuthor":true,"prefix":"","firstName":"Ghaithaa","middleName":"","lastName":"Hamoud","suffix":""},{"id":614890858,"identity":"3d0c16e7-74d7-479a-9614-8a758fb85783","order_by":1,"name":"Gennadiy Kamaev","email":"","orcid":"","institution":"Institute of Semiconductor Physics","correspondingAuthor":false,"prefix":"","firstName":"Gennadiy","middleName":"","lastName":"Kamaev","suffix":""},{"id":614890861,"identity":"3db0e22e-c928-445f-bafa-68c5c874a66b","order_by":2,"name":"Michel Vergnat","email":"","orcid":"","institution":"University of Lorraine","correspondingAuthor":false,"prefix":"","firstName":"Michel","middleName":"","lastName":"Vergnat","suffix":""},{"id":614890865,"identity":"3904e086-deb6-4cc7-9586-9311bbbf1cfa","order_by":3,"name":"Vladimir Volodin","email":"","orcid":"","institution":"Institute of Semiconductor Physics","correspondingAuthor":false,"prefix":"","firstName":"Vladimir","middleName":"","lastName":"Volodin","suffix":""}],"badges":[],"createdAt":"2026-03-24 09:08:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9209454/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9209454/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105944418,"identity":"9660e065-58f0-4715-a9a0-c36a3aa8003b","added_by":"auto","created_at":"2026-04-01 16:26:24","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":312918,"visible":true,"origin":"","legend":"\u003cp\u003eI-V characteristics (in dark and under illumination regime1) of samples: (a) - S1p; (b) - S1n; (c) - S2p; (d) - S2n.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9209454/v1/2322e820b922ef53d53b44a5.png"},{"id":105944496,"identity":"7e3238ac-8d88-486e-a59e-aa590b04bdb9","added_by":"auto","created_at":"2026-04-01 16:26:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":79224,"visible":true,"origin":"","legend":"\u003cp\u003eResponsivity of sample S2n as a function of reverse bias (illumination regime 1).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9209454/v1/bb1e14fb181e6c231639accd.png"},{"id":105944462,"identity":"5ac87e5d-bdbf-4935-83ce-213e11729a5d","added_by":"auto","created_at":"2026-04-01 16:26:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":165777,"visible":true,"origin":"","legend":"\u003cp\u003eThe \u003cstrong\u003eresponsivity\u003c/strong\u003e (a) and specific detectivity (b) of sample S2n at a reverse bias of -10 V as a function of wavelength (illumination regime 2).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9209454/v1/7a4649de38255a80ca755c9c.png"},{"id":107006411,"identity":"a1b71453-63b8-4525-b1ab-82c8596e69d0","added_by":"auto","created_at":"2026-04-15 16:26:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":900350,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9209454/v1/a204d73b-c1a0-4916-bf0b-fefb6c4137f8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Highly sensitive ITO/GeSiхOу/n-Si MIS photodiode with wide spectral range","fulltext":[{"header":"Introduction","content":"\u003cp\u003eModern digital electronics is based on metal-insulator-semiconductor (MIS) structures, which are also widely used in optoelectronics, such as Charge-Coupled Devices (CCDs) and Complementary Metal-Oxide-Semiconductor (CMOS) sensor cameras. Highly sensitive photodetectors (single and matrix) are also fabricated using p-n junctions. However, for over 50 years, efforts have continued to create highly sensitive photodetectors based on MIS structures with tunnel-thin dielectrics [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe main challenge in developing highly sensitive MIS Schottky barrier photodiodes is to control and reduce the dark current without reducing the photocurrent. Tunnel-thin dielectrics with precisely controlled thickness are used for this purpose. Recently, MIS photodiodes based on a thin silicon dioxide layer (4 nm) have been fabricated with ultra-low dark current and a wide photodetection range from 265 to 2200 nm [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The use of a bilayer dielectric opens the possibility of extending the photosensitivity range to short-wavelength UV. Solar-blind photodetectors based on MIS structures using silicon oxide and germanium oxide have been created; silicon oxide helped to reduce the dark current, and germanium oxide served as a photosensitive layer [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. To expand the spectral range, Ge and Si quantum dots [7; 8; 9], and silicon quantum nanolayers were introduced into the SiO\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e matrix [10;11].\u003c/p\u003e \u003cp\u003eAn alternative to tunnel-thin dielectrics are non-stoichiometric dielectrics, which exhibit other mechanisms of electron transport (not only sub-barrier tunneling), for example, SiO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e, which is used in perspective memory elements - memristors, as well as in photomemristors [1; 13]. Recently, interest has arisen in non-stoichiometric germanium oxide GeO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e, in which the memristor effect has also been discovered [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. A mixture of silicon and germanium oxides in the form of non-stoichiometric germanosilicate glasses (GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e) allows one to vary the transport properties by changing the stoichiometric parameters \u003cem\u003ex\u003c/em\u003e and \u003cem\u003ey\u003c/em\u003e. Memristors and photomemristors have been fabricated from GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e [15; 16]. In our previous studies, we demonstrated the photosensitivity of GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e-based MIS structures [\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In this study, we developed for the first time an ITO/GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e/n-Si-based MIS photodiode with high specific detectivity in the UV, visible, and near-IR ranges, comparable to that of silicon p-n junction photodiodes.\u003c/p\u003e"},{"header":"Experimental part","content":"\u003cp\u003eIn this work, thin GeSi\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e films were obtained by electron beam physical vapor deposition (EB-PVD) under high vacuum conditions. The targets (GeO₂ and SiO₂ powders) were co-evaporated simultaneously using electron beams. The initial pressure in the chamber was (10⁻⁹\u0026ndash;10⁻⁸) Torr, but during the evaporation of the targets it increased to 10⁻⁷\u0026ndash;10⁻⁶ Torr. The evaporated material was deposited on two types of substrates: the first was n-type Si CZ (100) (phosphorus-doped), with a specific resistivity ρ in the range 6 to 8 Ohm\u0026middot;cm; the second was p-type Si CZ (100) (boron-doped), with a resistivity ρ in the range 10 to12 Ohm\u0026middot;cm. Before being placed in the vacuum chamber, the native oxide layer was removed from the Si substrates by hydrofluoric acid etching. However, the substrates were kept in air for one to two hours, allowing the formation of a \"fresh\" layer of native oxide. Evaporated components from two targets (GeO₂ and SiO₂ powders) were deposited on the substrate, such that the composition of the deposited film was [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e1\u0026minus;z\u003c/em\u003e\u003c/sub\u003e, where the z parameter was set by controlling the evaporation rate of each target. It should be noted that during the evaporation of GeO\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e powders, due to the different volatility of the Ge, GeO, O\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e, and GeO\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e components, a film of the composition GeO\u003csub\u003e\u003cem\u003e1.1\u0026divide;1.2\u003c/em\u003e\u003c/sub\u003e is deposited [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. A quartz microbalance sensor above each source was used to control the deposition rate, which enabled the determination of the evaporation regime for the deposition of a film with the composition [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e. Films of this composition were deposited onto n- and p-Si substrates by a unique \"side-by-side\" deposition process. The thickness, structural properties, and composition of this sample were previously determined using spectral ellipsometry, Fourier Transform Infrared (FTIR) spectroscopy, Raman scattering (RS) spectroscopy, and X-ray photoelectron spectroscopy (XPS), as described in detail in [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. According to ellipsometry data, the thickness of the native silicon oxide layer was 2.5 nm, and the thickness of the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e film was 104 nm. RS spectroscopy data indicate that the film does not contain clusters of amorphous or crystalline germanium [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. An analysis of the FTIR-absorption results showed that the film contains the following chemical bonds: Ge-O, Si-O, Si-O-Ge. According to XPS data, the z parameter in the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003ez\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e1\u0026minus;z\u003c/em\u003e\u003c/sub\u003e film was 0.74, and the film contained 11at.% silicon, 53at.% oxygen, 4at.% carbon, and 32at.% germanium [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Thus, the parameter ν is in the range1.1-1.2. To study the influence of the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer on the photosensitive properties of the MIS structure, reference samples were fabricated without this layer, but only with a thin layer of native oxide (Fig. S1a, b). For electrical measurements, top contacts of indium tin oxide (ITO) with a thickness of 150 to 200 nm and a sheet resistance of 40 to 80 Ohm/□ were deposited on the samples by magnetron sputtering through a mask. The size of the contact pads was 0.7 by 0.7 mm. Ohmic contact with the back side of the silicon substrate was achieved by rubbing it with an indium-gallium (In-Ga) paste. The structure was then placed on a copper plate. During the experiments, this side was at zero potential, while a positive or negative bias was applied to the top ITO electrode. A schematic diagram of the MIS structures for all samples is shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea\u0026ndash;d. The spectral dependencies of the photosensitivity were studied using a monochromator (Nanotechnology Center, Novosibirsk, Russia) in the wavelength range of 400 to 1100 nm (spectral resolution of 8 nm). A halogen lamp was used as the radiation source. To suppress the influence of second-order diffraction radiation during measurements in the wavelength range above 580 nm, a special edge filter was used. Two illumination regimes were applied to the samples. Regime 1: the monochromator was set to the zero-diffraction order (thus, the whole spectrum of the halogen lamp reached the sample), the total power reaching the contact pad was 500 \u0026micro;W, which corresponds to a fluence of 1 kW/m\u0026sup2;. Regime 2: the monochromator was set to the first order of diffraction (the sample was illuminated by quasi-monochromatic light); at the maximum spectral power, the fluence was 1.6 W/m\u0026sup2;. In the UV region, measurements were carried out using a 368 nm Light Emitting Diode (PK2B-3LLE-GNVS, 200 mW peak power) and a narrow-bandpass filter that suppresses visible light.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eFigures \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb show the current-voltage characteristics (I-V characteristics) in the voltage range of \u0026plusmn;\u0026thinsp;5 V for MIS structures without a [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer on p- and n-type substrates (samples S1p and S1n, respectively) in the dark (black curve) and under illumination by a halogen lamp in regime 1 (red curve). It can be seen that for sample S1p under reverse bias (+\u0026thinsp;5 V), the photocurrent is 8.6 times greater than the dark current, and the dark I-V characteristic demonstrates a diode behavior (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). For the sample on the n-type substrate (S1n) under reverse bias (-5 V), the leakage current is high, so the dark current is almost equal to the photocurrent (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The I-V characteristics in the dark of the samples with the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer on p- and n-type substrates (samples S2p and S2n, respectively), shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, exhibit diode characteristics. Reverse bias (creating a depletion space charge region (SCR) in the semiconductor substrate) is positive for p-Si and negative for n-Si [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For the dark I\u0026ndash;V characteristic of the S2p sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), one can see that the minimum current does not correspond to zero bias voltage, probably due to the presence of a built-in charge either in the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer or at its interfaces. The main result of adding the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer is a significant decrease in the dark current under reverse bias. Thus, for p-Si structures under reverse bias (+\u0026thinsp;5 V), the dark current decreases by two orders of magnitude (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), and for n-Si structures under reverse bias (-5 V), the dark current decreases by four orders of magnitude (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Moreover, for structures on p-Si with reverse bias (+\u0026thinsp;5 V), the photocurrent decreases by only a factor of six (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), and for structures on n-Si with reverse bias (-5 V), the photocurrent decreased by only a factor of 3.5 (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003eSince the S2n sample demonstrated the best ratio of photocurrent to dark current, its photoelectric characteristics were further investigated in more details. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the dependence of its responsivity on voltage under illumination regime 1. Using the methodology described at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.hamamatsu.com/eu/en/product/optical-sensors/photodiodes.html\u003c/span\u003e\u003cspan address=\"https://www.hamamatsu.com/eu/en/product/optical-sensors/photodiodes.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e, the external quantum efficiency can be calculated from the responsivity. The spectral maximum of the halogen lamp's radiation power occurs at a wavelength of 650 nm (photon energy of 1.9 eV). For photons of this energy, with an external quantum efficiency of 100% (i.e., one incident photon generates one electron-hole pair), the responsivity is 0.5 A/Watt. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows that for the S2n sample, at a reverse bias greater than 2.2 V, the external quantum efficiency exceeds 100%, i.e., a photocurrent multiplication occurs. The mechanism of photocurrent multiplication could be either the avalanche effect [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], or the effect of inhomogeneities in the dielectric, for example, \"paths\" in the native oxide layer [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e also shows an increase in responsivity with increasing reverse bias with two plateaus. The maximum responsivity is observed in the reverse bias range from \u0026minus;\u0026thinsp;8.5 to -10 V, while (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed) the dark current remains almost unchanged. Therefore, a bias of -10 V was chosen for investigating the spectral characteristics of the photosensitivity.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea shows the responsivity dependence on wavelength in the range from UV to IR for the S2n sample at a reverse bias of -10 V, illumination regime 2. The maximum responsivity was observed in the wavelength range of 700 and 750 nm, with its value exceeding the data obtained in references [\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9 CR10\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Moreover, this value significantly exceeds the result obtained in a previous work using a dielectric film (GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e) of different composition and containing a thin germanium layer [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. It is also worth noting that, in illumination regime 2, the responsivity values in the wavelength range from 400 to 1050 nm exceed those obtained with illumination in regime 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This indicates a nonlinear dependence of the photocurrent on the fluence, since, in regime 1, it is three orders of magnitude greater than in regime 2.\u003c/p\u003e \u003cp\u003eThe mechanism of photocurrent generation has been discussed earlier [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For photons in the visible and near-IR ranges, it involves absorption in the depletion SCR of the silicon substrate. However, in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, a local responsivity peak appears at a wavelength of 450 nm. This peak can be explained by light absorption associated with defects in the GeSi\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003ey\u003c/em\u003e\u003c/sub\u003e dielectric layer, in particular with oxygen vacancies. These defects create local energy levels in the band gap, which leads to the appearance of a photoluminescence peak in this spectral region and facilitates the generation of photocarriers even with a low absorption coefficient [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe estimate that the dominant noise in the dark current is shot noise, since the fluctuation of the dark current caused by thermal noise at a reverse bias of -10 V, even at high frequencies (1 MHz), is very small (2.47\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;17\u003c/sup\u003e A). Walter Schottky defined the value of shot noise as the root-mean-square variance of current \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{I}_{Shot}^{2}=2eI\\:{\\Delta\\:}f\\)\u003c/span\u003e\u003c/span\u003e [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Delta\\:}f\\)\u003c/span\u003e\u003c/span\u003e is the bandwidth, \u003cem\u003ee\u003c/em\u003e \u0026ndash;is the electron charge, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:I\\)\u003c/span\u003e\u003c/span\u003e is the current value. In our case, the following expression was used to calculate the specific detectivity: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{D}^{*}=\\frac{{S}_{I}\\sqrt{A\\bullet\\:{\\Delta\\:}f}}{\\sqrt{2\\text{e}{I}_{dark}\\:{\\Delta\\:}\\text{f}\\:}}=\\frac{{S}_{I}\\sqrt{A}}{\\sqrt{2\\text{e}{I}_{dark}\\:}}\\)\u003c/span\u003e\u003c/span\u003e [24; 25], where S\u003csub\u003e\u003cem\u003eI\u003c/em\u003e\u003c/sub\u003e is the current responsivity and \u003cem\u003eA\u003c/em\u003e is the ITO contact area. The specific detectivity \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{D}^{*}\\)\u003c/span\u003e\u003c/span\u003e is measured in Jones [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb shows the wavelength dependence of the specific detectivity of the S2n sample at -10 V. All values over a wide spectral range (from 368 nm to 1100 nm) exceed 10\u0026sup1;\u0026sup2; Jones, with the highest value observed at a wavelength of 750 nm (7\u0026middot;10\u003csup\u003e12\u003c/sup\u003e Jones). All these values significantly exceed the data for MIS photodiodes obtained in previous works, which used SiO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e with various inclusions [5-11; 19; 25; 27].\u003c/p\u003e \u003cp\u003eThe obtained high specific detectivity values are mainly due to the strong suppression of the dark current when adding the [GeO\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.75\u003c/em\u003e\u003c/sub\u003e[SiO\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e\u003cem\u003e0.25\u003c/em\u003e\u003c/sub\u003e layer (by four orders of magnitude for n-Si). As shown by the \u0026ldquo;\u003cem\u003eab-initio\u003c/em\u003e\u0026rdquo; calculation of the band offset in the Ge/GeO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e system [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], the barrier for holes (2.8\u0026ndash;3.7 eV) in this system is much higher than the barrier for electrons (0.4\u0026ndash;1.1 eV), depending on \u003cem\u003ex\u003c/em\u003e. The band offset between Ge and Si is not large, approximately 0.4 eV for holes (for epitaxial heterostructure). Therefore, the barrier for holes in the Si/GeO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e system is also much higher than the barrier for electrons. Under reverse bias in n-type silicon, electrons move against the electric field, i.e., toward the bottom contact, while holes should move toward the top contact, but they are minority carriers, and their transport is suppressed due to the high barrier in the dielectric. As a result, the dark current is suppressed. Under illumination, the depletion SCR depth decreases [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], reducing the voltage drop across the substrate. However, the voltage drop across the dielectric layer increases, increasing the electron component of the current, i.e. the contribution of electrons injected from the top ITO contact. This compensates for the decrease in hole current, so that the photocurrent decreases by a factor of only a factor of 3.5 compared to the structure without a germanosilicate glass layer \u0026ndash; S1n.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, the MIS photodiode based on non-stoichiometric germanosilicate glass has been fabricated, and its spectral photosensitivity has been studied over a wide spectral range. Experiments demonstrate its high sensitivity and responsivity, as well as its relatively low dark current, enabling a specific detectivity up to 7\u0026middot;10\u0026sup1;\u0026sup2; Jones. The introduction of a non-stoichiometric germanosilicate glass layer into the MIS structure opens the way to the development of low-cost, highly sensitive photodetectors without the need for p-n junctions.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eCompeting Interests\u003c/strong\u003e \u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the Ministry of Science and Higher Education of the Russian Federation under Project No. FSUS-2024-0020. Additional funding was provided through the state assignment (theme No. FWGW-2025-0023).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eG.A. Hamoud contributed toward conceptualization (equal); data curation (lead); formal analysis (equal); investigation (equal); writing \u0026ndash; original draft (equal); writing \u0026ndash; review \u0026amp; editing (equal). G. N. Kamaev contributed toward conceptualization (equal); data curation (supporting); formal analysis (equal); investigation (equal); writing \u0026ndash; original draft (supporting); writing \u0026ndash;review \u0026amp; editing (supporting). M. Vergnat contributed toward investigation (equal); writing \u0026ndash; review\u0026amp; editing (equal). V. A. Volodin contributed toward conceptualization (lead); data curation (equal); formal analysis (equal); funding acquisition (lead); investigation (equal); project administration (equal); supervision (lead); writing \u0026ndash; original draft (lead); writing \u0026ndash; review \u0026amp; editing (lead).\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors acknowledge the Shared Research Center \u0026ldquo;VTAN\u0026rdquo; of Novosibirsk State University.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e \u003cli\u003e\u003cspan\u003eB.L. Sharma, \u003cem\u003eMetal-Semiconductor Schottky Barrier Junctions and Their Applications\u003c/em\u003e (Springer Science \u0026amp; Business Media, 2013)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA.Y. Vul\u0026rsquo;, A.T. 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Phys. \u003cb\u003e5\u003c/b\u003e(0065\u0026ndash;2539), 1\u0026ndash;96 (1953)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZ. Huang, Y. Mao, G. Lin et al., Low dark current broadband 360\u0026ndash;1650 nm ITO/Ag/n-Si Schottky photodetector. Opt. Express. \u003cb\u003e26\u003c/b\u003e, 5827 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ.F. Binder, P. Broqvist, A. Pasquarello, Electron trapping in sub-stoichiometric germanium oxide. Appl. Phys. Lett. \u003cb\u003e97\u003c/b\u003e(9), (2010)\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9209454/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9209454/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, we present a highly sensitive photodiode based on an ITO/GeSi\u003csub\u003e\u003cem\u003eх\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003eу\u003c/em\u003e\u003c/sub\u003e/n-Si structure without a p-n junction. The GeSi\u003csub\u003e\u003cem\u003eх\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e\u003cem\u003eу\u003c/em\u003e\u003c/sub\u003e dielectric layer plays a key role in reducing the dark current by four orders of magnitude compared to ITO/n-Si structures containing only native Si oxide, while the photocurrent decreases only slightly. High responsivity and specific detectivity covering the UV to IR range have been achieved, enabling this structure to be used for detecting optical signals over a wide spectral range.\u003c/p\u003e","manuscriptTitle":"Highly sensitive ITO/GeSiхOу/n-Si MIS photodiode with wide spectral range","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-01 16:25:50","doi":"10.21203/rs.3.rs-9209454/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1ce87c88-80bd-4a8c-86be-986484543507","owner":[],"postedDate":"April 1st, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-15T16:25:36+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-01 16:25:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9209454","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9209454","identity":"rs-9209454","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}