Hydrogen sulphide doping of GaAs and AlxGa1−xAs grown by molecular beam epitaxy (MBE)

Abstract

H2S gas has been used during molecular beam epitaxy (MBE) growth of GaAs and Al x Ga1–x As as sulphur vector forn-type doping. Doping efficiencies are less than 10–3 at usual growth temperatures, and are limited by an incorporation competitive surface process, probably 2Ga+H2S→Ga2S+H2. In AlxGa1–x As forx >= 0.2 the doping efficiency is further reduced by carrier freeze-out at deep levels. Measured thermal activation energies depend on growth conditions and remain relatively low even up to the direct-indirect bandgap crossover for substrate temperatures in the 585–645 ‡C range.