Compensation effects in Si-doped GaAs grown by molecular beam epitaxy

Abstract

The effect of varying As4/Ga flux ratio during growth on the incorporation of Si as a dopant in GaAs grown by molecular beam epitaxy (MBE) has been studied by low-temperature mobility and carrier concentration measurements. In the low residual doping range (n≤1×1015 cm−3), electron mobilities increase with increasing As4 flux; this increase may be related to the reduced incorporation of compensating C acceptors. Highest mobility achieved was μ(55 K)=97 600 cm2/Vs at a background pressure of ∼2×10−6 Torr. At Si doping levels ≥1016 cm−3, both carrier concentration and mobility were found to be independent of As4 pressure over the range of our experiments ( pAs4 ∼0.9–6×10−6 Torr). We conclude, contrary to previous findings, that Si autocompensation effects have only a minor influence on the electrical properties of MBE GaAs layers under the usual growth conditions.