IMPROVED ELECTRON-MOBILITY OF 2-DIMENSIONAL ELECTRON-GAS FORMED AREA-SELECTIVELY IN GAAS/ALGAAS HETEROSTRUCTURE BY FOCUSED SI ION-BEAM IMPLANTATION AND MBE OVERGROWTH

We studied the effects of annealing and the Si implantation dose on the electrical properties of two-dimensional electron gases formed area-selectively in GaAs/Al(x)Ga(1-x)As (x = 0.3) herterostructures by focused Si ion beam implantation into AlGaAs and GaAs MBE overgrowth. The implanted Si was electrically activated by rapid thermal annealing (RTA: 1000-degrees-C, 6 s). We found that pre-annealing at 600-degrees-C for 30 minutes prior to the RTA suppresses Si outdiffusion into the GaAs channel layer, and that lower implantation doses produce higher electron mobilities. We also found that low energy implantation and pre-annealing at 600-degrees-C for one hour before MBE overgrowth improve electron mobility. We obtained an electron mobility of 32000 cm2/V.s at 77 K with a Si dose of 2 x 10(12) cm-2.