Some GaAs solar cells degrade when exposed to high reverse currents. The degradation is significantly reduced when G e substrates are used instead of GaAs substrates for MOCVD growth of the GaAs cell layers. We compare the performance of GaAs/GaAs and GaAs/Ge cells before and after reverse current stress testing. Diode measurements (dark and illuminated), infrared thermography and crystal defect delineation were used to analyze the cell performance. A three-dimensional computer model for temperature distribution with the cells during testing added insight. The possible effect of the conclusions on advanced GaAs cell design is discussed.
BACKGROUND