Improvement of Heterointerface Properties of GaAs Solar Cells Grown With InGaP Layers by Hydride Vapor-Phase Epitaxy

It is crucial to develop a low-cost growth system to implement large-scale terrestrial modules in III-V solar cells. Hydride vapor-phase epitaxy (HVPE) has emerged as a low-cost alternative for the fabrication of III-V solar cells. However, it is difficult to utilize HVPE to fabricate abrupt GaAs-on-InGaP heterointerfaces. During growth interruption, indium segregation and exchange between arsenic and phosphorous atoms occur easily on the InGaP surface. The growth sequence is dependent on the reactor configuration. In this study, we investigated the growth sequence in a triple-chamber HVPE system to improve the abruptness of the heterointerfaces of GaAs solar cells. It was found that a short interruption of growth under flowing phosphine is critical in eliminating the InGaAsP interlayer at the interface between the p-InGaP back surface layer and the p-GaAs base layer. This improved cell efficiency to 20.87% for the upright cell and to 22.10% for the inverted front-junction cell.