Si as an acceptor in (110) GaAs for high mobility p-type heterostructures

We implement metallic layers of Si-doped (110) GaAs as modulation doping in high mobility p-type heterostructures, changing to p-growth conditions for the doping layer alone. The strongly auto-compensated doping is first characterized in bulk samples, identifying the metal-insulator transition density and confirming classic hopping conduction in the insulating regime. To overcome the poor morphology inherent to Si p-type (110) growth, heterostructures are fabricated with only the modulation doping layer grown under p-type conditions. Such heterostructures show a hole mobility of $\mu = 1.75 \times10^5~ \textnormal{cm}^2/\textnormal{V}\textnormal{s}$ at density $p=2.4\times10^{11}~ \textnormal{cm}^{-2}$. We identify the zero field spin-splitting characteristic of p- type heterostructures, but observe a remarkably isotropic mobility and a persistent photoconductivity unusual for p- heterojunctions grown using other doping techniques. This new modulated growth technique is particularly relevant for p-type cleaved-edge overgrowth and for III-V growth chambers where Si is the only dopant.