Enhanced performance in AlGaN deep-ultraviolet laser diodes without an electron blocking layer by using a thin undoped Al0.8Ga0.2N strip layer structure

Enhanced performance in AlGaN deep-ultraviolet laser diodes without an electron blocking layer by using a thin undoped Al0.8Ga0.2N strip layer structure | 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 Enhanced performance in AlGaN deep-ultraviolet laser diodes without an electron blocking layer by using a thin undoped Al 0.8 Ga 0.2 N strip layer structure Xien Sang, Fang Wang, Juin J. Liou, Yuhuai Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6126558/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 AlGaN-based deep ultraviolet laser diodes (DUV LD) often use electron blocking layers (EBL) to prevent electron leakage into the p-type region. However, EBL can also impede the injection of holes into the active region, resulting in a reduction of laser efficiency. To address this issue, we propose using an undoped thin Al 0.8 Ga 0.2 N strip structure after the last quantum barrier (LQB) instead of the EBL. Our results show that the 1 nm Al 0.8 Ga 0.2 N strip layer can effectively suppress electron leakage and enhance hole injection by increasing the effective barrier height when compared to conventional laser designs with EBLs. This improved efficiency results in a higher carrier concentration in the active region, higher recombination efficiency in the quantum well, and a significant increase in the output power of the laser. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 introduction The current deep ultraviolet (DUV) laser diode (LD) exhibits significant potential for a range of applications, including transportation, bio-detection, medical phototherapy, and water purification [1-5]. Compared to conventional mercury lamps, DUV LDs offer advantages such as extended lifespan, enhanced energy efficiency, and environmental sustainability [6-8]. Consequently, these devices have garnered increasing attention from researchers over recent decades. However, a notable challenge remains: a substantial decline in device performance with increasing current, which continues to hinder their application in high-power contexts [9,10]. Several factors have been identified as contributing to this efficiency degradation, including electron leakage [11,12], low hole injection efficiency [13], high carrier dislocation density [14], and Auger recombination [15-17], The higher mobility of electrons relative to holes results in electron spillover and significant energy loss [18,19]. To address these issues, a variety of solutions have been proposed. For instance, the use of dilute-As GaNAs has been suggested to reduce interband Auger recombination [20]. Additionally, to mitigate electron leakage and enhance carrier injection, approaches such as the substitution of AlGaN with BGaN material for electron leakage prevention [21], Zhang et al. designed the symmetrical step-shaped electron and hole blocking layers (HBL) [22], Wang et al. designed a double-tapered EBL [23]. However, introducing an EBL with a high aluminum component can only alleviate the electron leakage problem to a certain extent. The ionization energy of Mg-doped AlGaN layers is enhanced with the increase of Al content. Achieving high p-type conductivity in a high Al content AlGaN layer is difficult. As a result, the hole concentration in the p-region is limited [24]. Furthermore, polarized charge regions can form at the interface between the EBL and the QW, leading to electron accumulation near the last QW of the p-type layer, thereby exacerbating electron leakage. Additionally, the lattice mismatch between the final potential barrier layer and the EBL induces strong polarization effects, resulting in severe energy band bending in the EBL [25], This bending reduces the effective electron barrier height while increasing the effective hole barrier height, making hole injection into the active region more difficult. To address these issues, several researchers have proposed EBL-free structures. For example, Zhang et al. eliminated the EBL by utilizing p-type doped barriers and low Al mole fraction HBLs to improve light-emitting diode (LED) performance [26], Jain et al. using graded staircase barriers without EBL to enhance the efficiency of hole injection [27], Xiong et al. designed using AlGaN step-like barriers without EBL structure to improve blue LED characteristics [28], Sharif et al. proposed the structure of graded hole source layer without EBL to improve the performance of deep-ultraviolet nanowire LED [29], Velpula et al. proposed improving carrier transport in AlGaN deep-ultraviolet LED using a strip-in-a-barrier structure [30]. However, most studies focusing on EBL removal are centered on LED applications, with few addressing LDs. In this work, We propose a structure that eliminates the electron blocking layer (EBL) under the condition of a 267 nm emission wavelength. By removing the traditional EBL layer, this structure effectively reduces the band bending caused by polarization effects. Furthermore, the introduction of an undoped thin strip layer reduces the quantum confined Stark effect (QCSE) in the active region [31], ncreases the electron barrier height, and prevents electron leakage from the active region to the p-type region, thereby improving the stability and efficiency of the laser, particularly in high-power applications. Experimental comparative analysis shows that this structure also lowers the hole barrier height, facilitating hole injection, which effectively enhances carrier injection and recombination efficiency, thus improving the laser performance and mitigating efficiency degradation. Finally, we optimized the thickness of the thin layers (1 nm, 2 nm, 3 nm, 4 nm) and the Al composition (0.6, 0.65, 0.7, 0.75, 0.8). Our findings indicate that a 1 nm Al 0.8 Ga 0.2 N thin layer structure optimally enhances device performance, playing an important role in advancing high-power deep ultraviolet laser applications. 2 Simulation structure and parameters Figure 1 (a) is a schematic diagram of a DUV LD using sapphire as the substrate. The laser structure consists of a 0.1-µm-thick \(\:{\text{Al}}_{\text{0.75}}{\text{Ga}}_{\text{0.25}}\text{N}\) contact layer, a 1-µm-thick \(\:{\text{Al}}_{\text{0.75}}{\text{Ga}}_{\text{0.25}}\text{N}\) cladding (n-CL), a 0.11-µm-thick \(\:{\text{Al}}_{\text{0.68}}{\text{Ga}}_{\text{0.32}}\text{N}\) lower waveguide layer (LWG), multiple quantum wells (MQWs) composed of two 3-nm thick \(\:{\text{Al}}_{\text{0.58}}{\text{Ga}}_{\text{0.42}}\text{N}\) wells (QWs) and three 8-nm-thick \(\:{\text{Al}}_{\text{0.68}}{\text{Ga}}_{\text{0.32}}\text{N}\) barriers (QBs),The P-type region includes a 20-nm-thick \(\:{\text{Al}}_{\text{0.7}}{\text{Ga}}_{\text{0.3}}\text{N}\) EBL, a 0.7-µm-thick \(\:{\text{Al}}_{\text{0.68}}{\text{Ga}}_{\text{0.32}}\text{N}\) upper waveguide (UWG), a 0.4-µm-thick \(\:{\text{Al}}_{\text{0.75}}{\text{Ga}}_{\text{0.25}}\text{N}\) cladding (p-CL) and a 0.1-µm-thick \(\:{\text{Al}}_{\text{0.8}}{\text{Ga}}_{\text{0.2}}\text{N}\) contact layer. Based on the original LD1 structure. Insert a 1 nm thick \(\:{\text{Al}}_{\text{0.8}}{\text{Ga}}_{\text{0.2}}\text{N}\) undoped thin layer between the LQB and the EBL for LD2 structure. The LD3 structure is based on the LD2 structure with the EBL removed. The structure diagram of LD1, LD2, and LD3 is shown in Fig. 1 (b). Analyze the optical and electrical properties of devices with the Advanced Physical Model for Semiconductor Devices (PICS3D) developed by Crosslight Software Inc [ 32 ]. PICS3D software calculates the electrical behavior of all LDs by solving Poisson’s equation and the current continuity equation for electrons and holes [ 33 ]. In this simulation, the p- and n-electrodes were considered ideal ohmic contacts. According to the experimental conditions, the ambient temperature is set to 300 K, the laser cavity length is 530 µm, the width is 3 µm, the return loss is 2400, and the specular refractive index is 30% [ 34 ]. Spontaneous polarization and piezoelectric polarization were carefully designed with the method proposed by Fiorentini et al. [ 35 ]. The LD structure is a Fabry– Perot cavity modified from the GaN blue LD proposed by Nakamura and Fasol [ 36 ]. Other detailed material parameters can be found in the reference [ 37 ]. 3 Simulation Results and Discussion To study the performance of the proposed structure, we conducted a numerical analysis to investigate the three LDs. First, we calculated the energy band diagrams of the LD1, LD2, and LD3. The principle of improving hole injection and electron leakage is to reduce the effective barrier height of the valence band and increase the effective barrier height of the conduction band [ 38 ]. The effective barrier height is defined as the energy difference between an energy band and its corresponding quasi-Fermi level [ 39 ]. It is a reliable parameter for evaluating a laser's electron confinement ability and hole injection efficiency. As illustrated in Fig. 2 , the electron effective barrier height for LD1 is 158.2 meV, which is relatively low compared to LD2, where an undoped strip thin layer has been incorporated. After eliminating the EBL, the effective potential barrier for LD3 rises to 420.7 meV, significantly hindering electron leakage. In contrast, the effective potential barrier for holes in LD3 is 62.8 meV, which is lower than that of LD1 (149.2 meV) and LD2 (261.2 meV), thereby minimizing the resistance to hole injection into the active region. This reduction in hole injection barrier primarily arises due to the polarization charge generated at the heterointerface between the LQB and the EBL, which causes a sharp band bending in the conduction band, thereby lowering the effective barrier height for electrons while simultaneously increasing the barrier for holes. Furthermore, this polarization effect results in the accumulation of electrons in this region, contributing to the formation of nonradiative recombination centers [ 40 ] thereby exacerbating electron leakage. Additionally, a hole depletion region forms at the LQB-EBL heterointerface due to the polarization effect, as shown in Fig. 2 (a), which further limits hole injection efficiency. However, the insertion of the thin strip layer mitigates the impact of this depletion region, creating a hole accumulation zone, as seen in Fig. 2 (b). In the absence of the EBL structure, LD3 eliminates the hole depletion region entirely, forming two distinct hole accumulation regions, as depicted in Fig. 2 (c), which further enhances hole injection efficiency. To further validate the proposed structure, we examine the electron and hole concentrations in the three LD configurations, as shown in Fig. 3 . The removal of the EBL in LD3 eliminates the energy band bending caused by the polarization charge, which in turn elevates the pulled-down energy band. This leads to an increase in the effective electron barrier height, thereby reducing electron leakage into the p-type region. As illustrated in Fig. 3 (a), the electron concentration in the p-type region of LD3 is the lowest when compared to LD1 and LD2. Additionally, LD3 reduces the effective hole barrier height, facilitating hole injection into the active region. As shown in Fig. 3 (b), the highest hole concentration is observed in the thin strip layer of LD3, which further supports our previous analysis. As a result, the output power of LD3 shows a significant improvement compared to LD1 and LD2. As demonstrated in Figs. 4 (a), and 4(b), the output power of LD3 increases to 100.2 mW, surpassing that of LD1 (87 mW) and LD2 (91 mW). Additionally, the slope efficiency of LD3 reaches 1.8 W/A, representing improvements of 12% and 8% over LD1 (1.6 W/A) and LD2 (1.7 W/A), respectively. Furthermore, the threshold current for LD3 is reduced to 24 mA, which is lower than that of LD1 (26 mA) and LD2 (25 mA), and the threshold voltage of LD3 is 4.623 V, which is also lower than that of LD1 (4.629 V) and LD2 (4.632 V). These improvements can be attributed to the higher carrier concentration in the active region of LD3, as shown in Figs. 5 (a), and 5(b). Additionally, in AlGaN-based materials, holes exhibit a relatively high effective mass and low mobility compared to electrons, leading to a non-uniform distribution of holes within the multiple quantum well (MQW) structure. Consequently, holes near the p-side of the MQW accumulate at higher concentrations than those near the n-side [ 41 , 42 ], which enhances the effective radiative recombination rate within the MQW, as illustrated in Fig. 5 (c). This increased radiative recombination in the active region leads to a lower threshold current for LD3, as shown in Fig. 5 (d), further improving the optoelectronic properties of the device. To gain deeper insight into the device performance, we calculated the electron and hole current densities for LD1, LD2, and LD3. As shown in Fig. 6 (a), the increased effective electron potential barrier height in LD3 significantly reduces electron leakage. In Fig. 6 (b), LD3, by removing the energy band bending caused by the polarization charge effect at the EBL-LQB interface, forms a hole accumulation region. This not only improves hole injection but also reduces the energy loss of holes during transport, leading to enhanced device performance. We further investigated the performance of LD2 with an inserted undoped thin strip structure of Al x Ga 1−x N, varying the Al component and thickness. As shown in Figs. 7 (a), and 7(b), the output power and radiative recombination rate of LD2 are maximized when the Al component is 0.8, yielding the best laser performance. This improvement is attributed to the insertion of the undoped thin strip structure between the EBL and the LQB of LD2, which effectively mitigates the band bending caused by polarization at the heterogeneous interfaces, thereby enhancing device performance. At lower Al components, however, the electron confinement in the QW weakens, leading to increased electron leakage into the p-region, which negatively impacts the radiative recombination rate. When the Al component is 0.8, the electron effective potential barrier is at its highest, leading to stronger electron confinement in the MQW. Furthermore, the formation of a hole accumulation region at the heterogeneous interface reduces the hole depletion region, thereby improving hole injection efficiency, increasing carrier concentration in the active region, and consequently enhancing the effective recombination rate and output power. Figures 7 (c), and 7(d) reveal that the device performance is optimized when the thickness of the Al₀.₈Ga₀.₂N thin strip structure is 1 nm. As the strip thickness increases, the ability of the cavities to enter the active region diminishes, reducing carrier injection efficiency and thereby lowering the effective recombination rate and output power. Therefore, the insertion of a 1 nm Al₀.₈Ga₀.₂N thin strip layer effectively reduces the impact of strong polarization effects, optimizing device performance. Building on these findings, we applied the conclusion to the removal of the EBL structure in LD3. As shown in Fig. 8 , the insertion of a 1 nm Al₀.₈Ga₀.₂N thin strip layer in LD3 further enhances device performance. This improvement is primarily due to the absence of the EBL layer in LD3, which prevents the strong polarization effects that typically lead to band bending. The thin strip layer increases the effective conduction band barrier height, better suppressing electron leakage, while simultaneously enhancing hole injection by inducing two hole accumulation regions at the thin layer. This significantly improves hole injection efficiency and overall device performance. Finally, Fig. 9 illustrates the electric field distribution at the heterojunction. In Fig. 9 (a), it is evident that the electric field at the heterojunction surface varies with different Al compositions, with the minimal electric field occurring at an Al composition of 0.8. Figure 9 (b) further analyzes the effect of thin layer thickness on the electric field when the Al composition is fixed at 0.8. It shows that the electric field at the heterojunction surface is minimal when the strip thickness is 1 nm. The electric field is closely related to the piezoelectric polarization charge density, and the small electric field at the heterogeneous interface reduces the polarization effect, thereby minimizing band bending, preventing electron leakage, and enhancing hole injection efficiency. Conclusion In this paper, we propose an EBL-free structure by incorporating an undoped thin strip layer to enhance the performance of DUV LDs. we observe a significant improvement in the device's performance. The effective electron barrier height for LD3 increases by 165.9%, from 158.2 meV to 420.7 meV, while the effective hole barrier height decreases by 58%, from 149.2 meV to 62.8 meV. As a result, the output power of LD3 increases by 14%, from 87.7 mW to 100.2 mW, and the threshold current is reduced. 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Lett. 92，053502 (2008), https://doi.org/10.1063/1.2839305 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6126558","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":423880334,"identity":"90b8a2a9-24cd-49de-ab7f-dcfd518eae27","order_by":0,"name":"Xien Sang","email":"","orcid":"","institution":"Zhengzhou University","correspondingAuthor":false,"prefix":"","firstName":"Xien","middleName":"","lastName":"Sang","suffix":""},{"id":423880335,"identity":"a025ca2e-43df-464d-b03b-a5a9c638ffc2","order_by":1,"name":"Fang Wang","email":"","orcid":"","institution":"Zhengzhou University","correspondingAuthor":false,"prefix":"","firstName":"Fang","middleName":"","lastName":"Wang","suffix":""},{"id":423880336,"identity":"bb5878bc-7560-4222-87e7-28bb78e9b3cd","order_by":2,"name":"Juin J. Liou","email":"","orcid":"","institution":"North Minzu University","correspondingAuthor":false,"prefix":"","firstName":"Juin","middleName":"J.","lastName":"Liou","suffix":""},{"id":423880337,"identity":"aa0b8933-7196-466e-9979-58dffc63a8a8","order_by":3,"name":"Yuhuai Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYBACNhB6YMAgB+cSpyXBgMGYeC1gZQkMDIkNRGvhY+8xe5BQcDh9fv8ZA4YPZYcZ+Gc3ELCC54y5QYLB4dzGhjMGjDPOHWaQuHOAgBaJHDMJkJZmxh4DZt62wwwGEgkEtMi/AWtJZ2PmMWD+S5QWCR6wlgQeNqAWRqK08KSVAbWkG87gYSs42HMunUfiBgEt8u2Ht0l8+GMtL99/eOODH2XWcvwzCGhhYOAwgDMPADEPIfVAwP6ACEWjYBSMglEwogEAw0c5Zeq9jpEAAAAASUVORK5CYII=","orcid":"","institution":"Zhengzhou University","correspondingAuthor":true,"prefix":"","firstName":"Yuhuai","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2025-02-28 08:08:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6126558/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6126558/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":77866196,"identity":"579ee4a6-d81a-419c-9d0e-e126f7a43ffa","added_by":"auto","created_at":"2025-03-06 09:26:48","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":130055,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematics of the DUV-LD structure, and (b) LD1, LD2, and LD3 structure diagram\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/b639127408025862a1d50d3a.png"},{"id":77866197,"identity":"161ce30e-271f-4663-b22c-2d527fffe4b0","added_by":"auto","created_at":"2025-03-06 09:26:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":70366,"visible":true,"origin":"","legend":"\u003cp\u003eEnergy band diagram and quasi-fermi level (a) LD1, (b) LD2, and (c) LD3\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/b6588eb8f50b5461ef36905c.png"},{"id":77864704,"identity":"cc410452-017d-4037-91c5-8717ceb80d27","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":56322,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Electron leakage in the p-type region of three structures, and (b) hole concentration of the three structures\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/26111d712851a9da3b265b49.png"},{"id":77864706,"identity":"364f152b-b584-4171-bf64-7a232aca2a4c","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":80130,"visible":true,"origin":"","legend":"\u003cp\u003e(a) P-I curve of three structures, and (b) I-V curve of three structures\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/7da628cf3bdd8531d7cff073.png"},{"id":77864712,"identity":"6827c940-41c0-4aed-b504-d06ffe844a11","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":83692,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The electron concentration in the MQWs, (b) the hole concentration in the MQWs, (c) stimulated recombination rate in MQWs, and (d) numerically calculated near-field optical model profile for LD1, LD2, and LD3\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/288cce03692737e5d0ffb570.png"},{"id":77864744,"identity":"c856c158-7373-40ac-a13b-e06bb470cad4","added_by":"auto","created_at":"2025-03-06 09:18:51","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":38021,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Electron current density of three structures, and (b) hole current density of three structures\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/1e92cb7619624d15843e7b33.png"},{"id":77864711,"identity":"9850253f-15df-4d82-a28d-0b96bc504b2d","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":92993,"visible":true,"origin":"","legend":"\u003cp\u003e(a) LD2 output power of different Al components, (b) LD2 recombination rates of different Al components in MQWs, (c) output power with different thickness of \u0026nbsp;Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN \u0026nbsp;strip of LD2, and (d) recombination rates with different thickness of Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN\u0026nbsp;\u0026nbsp;\u0026nbsp;strip of LD2 in MQWs\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/f75d239bf239a44a4959472d.png"},{"id":77864727,"identity":"c2bb5727-dff7-4ce2-af26-6223789ea49d","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":79509,"visible":true,"origin":"","legend":"\u003cp\u003e(a) LD3 output power of different Al components, (b) LD3 recombination rates of different Al components in MQWs, (c) output power with different thickness of Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN \u0026nbsp;strip of LD3, and (d) recombinationrates with different thickness of \u0026nbsp;Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN\u0026nbsp;\u0026nbsp;strip of LD3 in MQWs\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/517367760c9a060a97cb675f.png"},{"id":77864708,"identity":"3e6ed40f-a512-4826-b465-022b14791fb0","added_by":"auto","created_at":"2025-03-06 09:18:49","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":57946,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Electric field distribution of different al components of LD3, (b) Electric field distribution of LD3 with different thicknes\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/106ceec54e37b770c14d4bae.png"},{"id":79539459,"identity":"966f0f74-afba-457d-9fd5-d0c003455eaa","added_by":"auto","created_at":"2025-03-31 03:01:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":940150,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6126558/v1/6cec0547-b961-4ea8-b5e7-32ea10207500.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eEnhanced performance in AlGaN deep-ultraviolet laser diodes without an electron blocking layer by using a thin undoped Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN strip layer structure\u003c/p\u003e","fulltext":[{"header":"1 introduction ","content":"\u003cp\u003eThe current deep ultraviolet (DUV) laser diode (LD) exhibits significant potential for a range of applications, including transportation, bio-detection, medical phototherapy, and water purification [1-5]. Compared to conventional mercury lamps, DUV LDs offer advantages such as extended lifespan, enhanced energy efficiency, and environmental sustainability\u0026nbsp;[6-8]. Consequently, these devices have garnered increasing attention from researchers over recent decades. However, a notable challenge remains: a substantial decline in device performance with increasing current, which continues to hinder their application in high-power contexts [9,10]. Several factors have been identified as contributing to this efficiency degradation, including electron leakage\u0026nbsp;[11,12], low hole injection efficiency\u0026nbsp;[13], high carrier dislocation density\u0026nbsp;[14], and Auger recombination\u0026nbsp;[15-17], The higher mobility of electrons relative to holes results in electron spillover and significant energy loss\u0026nbsp;[18,19]. To address these issues, a variety of solutions have been proposed. For instance, the use of dilute-As GaNAs has been suggested to reduce interband Auger recombination\u0026nbsp;[20].\u0026nbsp;Additionally, to mitigate electron leakage and enhance carrier injection, approaches such as the substitution of AlGaN with BGaN material for electron leakage prevention\u0026nbsp;[21],\u0026nbsp;Zhang et al. designed the symmetrical step-shaped electron and hole blocking layers (HBL)\u0026nbsp;[22],\u0026nbsp;Wang et al. designed a double-tapered EBL\u0026nbsp;[23].\u0026nbsp;However,\u0026nbsp;introducing an EBL with a high aluminum component can only alleviate the electron leakage problem to a certain extent.\u0026nbsp;The ionization energy of Mg-doped AlGaN layers is enhanced with the increase of Al content. Achieving high p-type conductivity in a high Al content AlGaN layer is difficult. As a result, the hole concentration in the p-region is limited\u0026nbsp;[24].\u0026nbsp;Furthermore, polarized charge regions can form at the interface between the EBL and the QW, leading to electron accumulation near the last QW of the p-type layer, thereby exacerbating electron leakage. Additionally, the lattice mismatch between the final potential barrier layer and the EBL induces strong polarization effects, resulting in severe energy band bending in the EBL\u0026nbsp;[25], This bending reduces the effective electron barrier height while increasing the effective hole barrier height, making hole injection into the active region more difficult. To address these issues, several researchers have proposed EBL-free structures. For example, Zhang et al. eliminated the EBL by utilizing p-type doped barriers and low Al mole fraction HBLs to improve light-emitting diode (LED) performance\u0026nbsp;[26], Jain et al. using graded staircase barriers without EBL to enhance the efficiency of hole injection\u0026nbsp;[27], Xiong et al. designed using AlGaN step-like barriers without EBL structure to improve blue LED characteristics\u0026nbsp;[28], Sharif et al. proposed the structure of graded hole source layer without EBL to improve the performance of deep-ultraviolet nanowire LED\u0026nbsp;[29], Velpula et al. proposed improving carrier transport in AlGaN deep-ultraviolet LED using a strip-in-a-barrier structure\u0026nbsp;[30]. However, most studies focusing on EBL removal are centered on LED applications, with few addressing LDs. In this work, We propose a structure that eliminates the electron blocking layer (EBL) under the condition of a 267 nm emission wavelength. By removing the traditional EBL layer, this structure effectively reduces the band bending caused by polarization effects. Furthermore, the introduction of an undoped thin strip layer reduces the quantum confined Stark effect (QCSE) in the active region\u0026nbsp;[31], ncreases the electron barrier height, and prevents electron leakage from the active region to the p-type region, thereby improving the stability and efficiency of the laser, particularly in high-power applications. Experimental comparative analysis shows that this structure also lowers the hole barrier height, facilitating hole injection, which effectively enhances carrier injection and recombination efficiency, thus improving the laser performance and mitigating efficiency degradation. Finally, we optimized the thickness of the thin layers (1 nm, 2 nm, 3 nm, 4 nm) and the Al composition (0.6, 0.65, 0.7, 0.75, 0.8). Our findings indicate that a 1 nm Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN thin layer structure optimally enhances device performance, playing an important role in advancing high-power deep ultraviolet laser applications.\u003c/p\u003e"},{"header":"2 Simulation structure and parameters","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a) is a schematic diagram of a DUV LD using sapphire as the substrate. The laser structure consists of a 0.1-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.75}}{\\text{Ga}}_{\\text{0.25}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e contact layer, a 1-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.75}}{\\text{Ga}}_{\\text{0.25}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e cladding (n-CL), a 0.11-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.68}}{\\text{Ga}}_{\\text{0.32}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e lower waveguide layer (LWG), multiple quantum wells (MQWs) composed of two 3-nm thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.58}}{\\text{Ga}}_{\\text{0.42}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e wells (QWs) and three 8-nm-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.68}}{\\text{Ga}}_{\\text{0.32}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e barriers (QBs),The P-type region includes a 20-nm-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.7}}{\\text{Ga}}_{\\text{0.3}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e EBL, a 0.7-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.68}}{\\text{Ga}}_{\\text{0.32}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e upper waveguide (UWG), a 0.4-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.75}}{\\text{Ga}}_{\\text{0.25}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e cladding (p-CL) and a 0.1-\u0026micro;m-thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.8}}{\\text{Ga}}_{\\text{0.2}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e contact layer. Based on the original LD1 structure. Insert a 1 nm thick \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{Al}}_{\\text{0.8}}{\\text{Ga}}_{\\text{0.2}}\\text{N}\\)\u003c/span\u003e\u003c/span\u003e undoped thin layer between the LQB and the EBL for LD2 structure. The LD3 structure is based on the LD2 structure with the EBL removed. The structure diagram of LD1, LD2, and LD3 is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b). Analyze the optical and electrical properties of devices with the Advanced Physical Model for Semiconductor Devices (PICS3D) developed by Crosslight Software Inc [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. PICS3D software calculates the electrical behavior of all LDs by solving Poisson\u0026rsquo;s equation and the current continuity equation for electrons and holes [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In this simulation, the p- and n-electrodes were considered ideal ohmic contacts. According to the experimental conditions, the ambient temperature is set to 300 K, the laser cavity length is 530 \u0026micro;m, the width is 3 \u0026micro;m, the return loss is 2400, and the specular refractive index is 30% [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Spontaneous polarization and piezoelectric polarization were carefully designed with the method proposed by Fiorentini et al. [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The LD structure is a Fabry\u0026ndash; Perot cavity modified from the GaN blue LD proposed by Nakamura and Fasol [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Other detailed material parameters can be found in the reference [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"3 Simulation Results and Discussion","content":"\u003cp\u003eTo study the performance of the proposed structure, we conducted a numerical analysis to investigate the three LDs. First, we calculated the energy band diagrams of the LD1, LD2, and LD3. The principle of improving hole injection and electron leakage is to reduce the effective barrier height of the valence band and increase the effective barrier height of the conduction band [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. The effective barrier height is defined as the energy difference between an energy band and its corresponding quasi-Fermi level [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. It is a reliable parameter for evaluating a laser's electron confinement ability and hole injection efficiency.\u003c/p\u003e \u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the electron effective barrier height for LD1 is 158.2 meV, which is relatively low compared to LD2, where an undoped strip thin layer has been incorporated. After eliminating the EBL, the effective potential barrier for LD3 rises to 420.7 meV, significantly hindering electron leakage. In contrast, the effective potential barrier for holes in LD3 is 62.8 meV, which is lower than that of LD1 (149.2 meV) and LD2 (261.2 meV), thereby minimizing the resistance to hole injection into the active region. This reduction in hole injection barrier primarily arises due to the polarization charge generated at the heterointerface between the LQB and the EBL, which causes a sharp band bending in the conduction band, thereby lowering the effective barrier height for electrons while simultaneously increasing the barrier for holes. Furthermore, this polarization effect results in the accumulation of electrons in this region, contributing to the formation of nonradiative recombination centers [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] thereby exacerbating electron leakage.\u003c/p\u003e \u003cp\u003eAdditionally, a hole depletion region forms at the LQB-EBL heterointerface due to the polarization effect, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a), which further limits hole injection efficiency. However, the insertion of the thin strip layer mitigates the impact of this depletion region, creating a hole accumulation zone, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b). In the absence of the EBL structure, LD3 eliminates the hole depletion region entirely, forming two distinct hole accumulation regions, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c), which further enhances hole injection efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further validate the proposed structure, we examine the electron and hole concentrations in the three LD configurations, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The removal of the EBL in LD3 eliminates the energy band bending caused by the polarization charge, which in turn elevates the pulled-down energy band. This leads to an increase in the effective electron barrier height, thereby reducing electron leakage into the p-type region. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a), the electron concentration in the p-type region of LD3 is the lowest when compared to LD1 and LD2. Additionally, LD3 reduces the effective hole barrier height, facilitating hole injection into the active region. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b), the highest hole concentration is observed in the thin strip layer of LD3, which further supports our previous analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs a result, the output power of LD3 shows a significant improvement compared to LD1 and LD2. As demonstrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a), and 4(b), the output power of LD3 increases to 100.2 mW, surpassing that of LD1 (87 mW) and LD2 (91 mW). Additionally, the slope efficiency of LD3 reaches 1.8 W/A, representing improvements of 12% and 8% over LD1 (1.6 W/A) and LD2 (1.7 W/A), respectively. Furthermore, the threshold current for LD3 is reduced to 24 mA, which is lower than that of LD1 (26 mA) and LD2 (25 mA), and the threshold voltage of LD3 is 4.623 V, which is also lower than that of LD1 (4.629 V) and LD2 (4.632 V). These improvements can be attributed to the higher carrier concentration in the active region of LD3, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a), and 5(b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAdditionally, in AlGaN-based materials, holes exhibit a relatively high effective mass and low mobility compared to electrons, leading to a non-uniform distribution of holes within the multiple quantum well (MQW) structure. Consequently, holes near the p-side of the MQW accumulate at higher concentrations than those near the n-side [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e], which enhances the effective radiative recombination rate within the MQW, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c). This increased radiative recombination in the active region leads to a lower threshold current for LD3, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(d), further improving the optoelectronic properties of the device.\u003c/p\u003e \u003cp\u003eTo gain deeper insight into the device performance, we calculated the electron and hole current densities for LD1, LD2, and LD3. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a), the increased effective electron potential barrier height in LD3 significantly reduces electron leakage. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(b), LD3, by removing the energy band bending caused by the polarization charge effect at the EBL-LQB interface, forms a hole accumulation region. This not only improves hole injection but also reduces the energy loss of holes during transport, leading to enhanced device performance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe further investigated the performance of LD2 with an inserted undoped thin strip structure of Al\u003csub\u003ex\u003c/sub\u003eGa\u003csub\u003e1−x\u003c/sub\u003eN, varying the Al component and thickness. As shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a), and 7(b), the output power and radiative recombination rate of LD2 are maximized when the Al component is 0.8, yielding the best laser performance. This improvement is attributed to the insertion of the undoped thin strip structure between the EBL and the LQB of LD2, which effectively mitigates the band bending caused by polarization at the heterogeneous interfaces, thereby enhancing device performance. At lower Al components, however, the electron confinement in the QW weakens, leading to increased electron leakage into the p-region, which negatively impacts the radiative recombination rate. When the Al component is 0.8, the electron effective potential barrier is at its highest, leading to stronger electron confinement in the MQW. Furthermore, the formation of a hole accumulation region at the heterogeneous interface reduces the hole depletion region, thereby improving hole injection efficiency, increasing carrier concentration in the active region, and consequently enhancing the effective recombination rate and output power.\u003c/p\u003e \u003cp\u003eFigures \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(c), and 7(d) reveal that the device performance is optimized when the thickness of the Al₀.₈Ga₀.₂N thin strip structure is 1 nm. As the strip thickness increases, the ability of the cavities to enter the active region diminishes, reducing carrier injection efficiency and thereby lowering the effective recombination rate and output power. Therefore, the insertion of a 1 nm Al₀.₈Ga₀.₂N thin strip layer effectively reduces the impact of strong polarization effects, optimizing device performance.\u003c/p\u003e \u003cp\u003eBuilding on these findings, we applied the conclusion to the removal of the EBL structure in LD3. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the insertion of a 1 nm Al₀.₈Ga₀.₂N thin strip layer in LD3 further enhances device performance. This improvement is primarily due to the absence of the EBL layer in LD3, which prevents the strong polarization effects that typically lead to band bending. The thin strip layer increases the effective conduction band barrier height, better suppressing electron leakage, while simultaneously enhancing hole injection by inducing two hole accumulation regions at the thin layer. This significantly improves hole injection efficiency and overall device performance.\u003c/p\u003e \u003cp\u003eFinally, Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e illustrates the electric field distribution at the heterojunction. In Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(a), it is evident that the electric field at the heterojunction surface varies with different Al compositions, with the minimal electric field occurring at an Al composition of 0.8. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(b) further analyzes the effect of thin layer thickness on the electric field when the Al composition is fixed at 0.8. It shows that the electric field at the heterojunction surface is minimal when the strip thickness is 1 nm. The electric field is closely related to the piezoelectric polarization charge density, and the small electric field at the heterogeneous interface reduces the polarization effect, thereby minimizing band bending, preventing electron leakage, and enhancing hole injection efficiency.\u003c/p\u003e "},{"header":"Conclusion","content":"\u003cp\u003eIn this paper, we propose an EBL-free structure by incorporating an undoped thin strip layer to enhance the performance of DUV LDs. we observe a significant improvement in the device's performance. The effective electron barrier height for LD3 increases by 165.9%, from 158.2 meV to 420.7 meV, while the effective hole barrier height decreases by 58%, from 149.2 meV to 62.8 meV. As a result, the output power of LD3 increases by 14%, from 87.7 mW to 100.2 mW, and the threshold current is reduced. These improvements effectively suppress electron leakage and enable efficient hole injection, addressing the performance limitations of conventional devices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement:\u003c/strong\u003e Supported by National Nature Science Foundation of China (Grant No. 62174148), National Key Research and Development Program (NKRDP Grant No. 2022YFE0112000), Key Program for International Joint Research of Henan Province (Grant No. 231111520300).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e No data were generated or analyzed in the presented research. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest:\u003c/strong\u003e The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eY. 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Lett. 92，053502 (2008), https://doi.org/10.1063/1.2839305\u003c/li\u003e\n\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-6126558/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6126558/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAlGaN-based deep ultraviolet laser diodes (DUV LD) often use electron blocking layers (EBL) to prevent electron leakage into the p-type region. However, EBL can also impede the injection of holes into the active region, resulting in a reduction of laser efficiency. To address this issue, we propose using an undoped thin Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN strip structure after the last quantum barrier (LQB) instead of the EBL. Our results show that the 1 nm Al\u003csub\u003e0.8\u003c/sub\u003eGa\u003csub\u003e0.2\u003c/sub\u003eN strip layer can effectively suppress electron leakage and enhance hole injection by increasing the effective barrier height when compared to conventional laser designs with EBLs. This improved efficiency results in a higher carrier concentration in the active region, higher recombination efficiency in the quantum well, and a significant increase in the output power of the laser.\u003c/p\u003e","manuscriptTitle":"Enhanced performance in AlGaN deep-ultraviolet laser diodes without an electron blocking layer by using a thin undoped Al0.8Ga0.2N strip layer structure","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-06 09:18:43","doi":"10.21203/rs.3.rs-6126558/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":"49a3213f-8ba1-46a4-ae21-22333161619c","owner":[],"postedDate":"March 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-31T02:53:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-06 09:18:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6126558","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6126558","identity":"rs-6126558","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}