Evaluation of GaAs solar cells grown under different conditions via hydride vapor phase epitaxy

Abstract

In this study, we characterize the GaAs solar cells grown under different conditions using a custom-built atmospheric-pressure hydride vapor-phase epitaxy (HVPE) reactor. Under typical HVPE growth involving the decomposition of AsH3 to Asx, the growth rate is considerably dependent on the temperature and is limited to ~10 μm/h at a low deposition temperature of 660 °C because of the large kinetic barrier of 198 kJ/mol. Herein, we grow GaAs with a considerably lower kinetic barrier of 7 kJ/mol by suppressing the decomposition of AsH3 in the reactor. Further, we grew GaAs solar cells at an extremely high growth rate of 120 μm/h using uncracked AsH3. However, the open-circuit voltage (VOC) was reduced from 1.0 V for the cells grown at 8 μm/h under typical growth using Asx to 0.95 V for the cells grown at 120 μm/h using hydride-enhanced growth. The reduction in VOC was attributed to the modulation of both the doping profile and the abruptness of heterointerfaces. A small amount of residual gases, which presents at the growth surface after the growth of the p-InGaP back surface field layer, is prominently incorporated during the growth of the p-GaAs base layer upon hydride-enhanced growth due to the fast kinetics.