Differences in Si doping efficiency in tertiarybutylarsine, monoethylarsine and arsine for GaAs and AlGaAs grown by MOVPE

Abstract

We investigate differences in Si doping of GaAs and AIGaAs between group-V sources. Si2H6 and SiH4 doping dependence on growth temperature, V/III ratio, total flow rate, growth rate, and off angle of substrate orientation was examined using tertiarybu-tylarsine (TBAs), monoethylarsine (EtAs), and arsine with a horizontal atmospheric pressure reactor. With either dopant source, Si incorporation for films grown using TBAs or EtAs was always higher than that using arsine. Using silane, dependence of Si incorporation on growth temperature and total gas flow velocity is different between group-V sources. Using disilane, dependence on V/III ratio and total gas flow velocity is different between group-V sources. These results imply that gas phase reactions play an important role. From the kinetic simulation of the decomposition of group-V sources, we verified that the concentrations of AsH3, AsH2, and AsH in vapor near the substrate are quite different among group-V sources. AsH2 is dominant reactant when using TBAs. We propose that H2AsSiH3 (silylarsine) is formed by the reaction between AsH2 radical and SiH4 and silylarsine should contribute Si incorporation reactions, resulting in high Si incorporation efficiency with TBAs and EtAs. We also suggest that AsH3 inhibits Si incorporation.