Controlled formation of GaAs pn junctions during hydride vapor phase epitaxy of GaAs

Abstract

Interface formation in HVPE GaAs was investigated through the growth of multilayer test structures with alternately doped and undoped layers and subsequently, pn diode devices. Two growth procedures were used in device formation: continuous growth of all layers, and a growth interruption with simultaneous equilibration of new gas flows for subsequent layers. These junctions were probed using SIMS to determine the doping profiles and impurity incorporation near the interfaces and throughout the bulk of the layers. The junction I–V characteristics were measured with and without illumination to correlate the junction properties with the measured photovoltaic performance. It was discovered that the use of a growth interruption leads to doping transitions up to 6x narrower than samples grown without interruption. The growth interruption leads to an interfacial Si spike that is not observed in the uninterrupted samples during growth of GaAs doped with silane. This spike does not appear to degrade either the material quality or pn junction quality, and pn diodes grown with interruption have exhibited enhanced device efficiencies under solar simulation compared with devices grown without interruption, reaching efficiencies of up to 9.2% without the use of antireflective coatings.