A noval method of determining bias lights for spectral response measurement of GaAs multi-junction laser power converters and its applications

Quantitative electrical analysis of sub-cells is crucial for the designing of high-efficiency GaAs multi-junction laser power converters (MJLPCs). Spectral response (SR) measurement is the main mean of characterizing the electrical performance of sub-cell. However, all the sub-cells in GaAs MJLPCs have the same SR range, resulting that finding suitable bias lights to make the sub-cells current-limited is difficult for the SR measurement of GaAs MJLPCs. Here, we report a method of determining bias lights for the SR measurement of GaAs MJLPCs based on the variation rules of simulated short-circuit current densities with wavelengths in the sub-cells of GaAs MJLPCs. The method of determining bias lights is applicable to a variety of GaAs MJLPCs, including in original state, at high temperature or after high-energy particles irradiation. With the method of determining bias lights, the measured external quantum efficiency (EQE) curves of the 1st cell, the 2nd cell and the 3rd cell in a GaAs triple-junction LPC were successfully obtained. The work is anticipated to provide guidelines for further developments of high-efficiency and high-reliability III-V MJLPCs.