High mobility GaAs/AlAs/(211)Si structures grown by MBE

Abstract

The growth on the preferred (211) silicon surface has been accomplished utilizing an interfacial layer of 100 Å of AlAs. We report on the (i) surface preparation, (ii) arsenic rich growth and (iii) mobility measurements of the resultant GaAs/AlAs(211) Si structure. An arsenic rich initial growth was utilized, which resulted in a sharp 2×2 reconstructed GaAs surface. In comparison, a gallium rich surface resulted in antiphase domains and in worst case Ga rich modules. Surface oxides were desorbed at 800°C prior to deposition at a final substrate temperature of 600–610°C for GaAs and 700°C for AlAs. The deposition in both cases was initiated at 250°C. Undoped GaAs/AlAs/(211) Si structures resulted in room temperature mobility values of 5275–8000 cm 2/V·s. The mobility values were optimizing by varying the thickness of the AlAs. A thickness of 100–120 Å was found to be necessary to prevent compensation due to outdiffusion from the silicon substrate. The GaAs films were shown to be smooth without evidence of antiphase domains.