UC Berkeley

Low-cost methods of III-V deposition are an important component of making high-efficiency III-V solar cells cost-competitive for terrestrial applications. Here, we report the design and testing of a close-spaced vapor transport system for the growth of epitaxial GaAs films using solid precursors and HCl as the transport agent. Previous work on a related system demonstrated growth of high-quality GaAs using H2O as the transport agent, but the use of H2O generates oxide-related defects and limits material compatibility. The new design also enables independent handling of source and substrate material. The effect of process conditions on growth rate, surface morphology, and substrate-orientation-dependent growth is discussed. We demonstrate successful doping of Si and Zn with average transport efficiencies of approximately 30% and 20%, respectively, based on secondary-ion-mass-spectrometry data. Room-temperature hall mobilities approached those achieved for GaAs grown by metal-organic vapor phase epitaxy and water-based close-spaced vapor transport, 2210–3400 cm2 V−1 s−1 for n-GaAs and 70–110 cm2 V−1 s−1 for p-GaAs depending on dopant concentration. Initial results on doping and cross-contamination suggest this system should be capable of homoepitaxial growth of p-n junctions.