SPATIAL LOCALIZATION AND DIFFUSION IN delta-DOPED GaAs AND Al sub (x) Ga sub (1-x) As AND ITS APPLICATION TO ELECTRON- MOBILITY OPTIMIZATION IN SELECTIVELY DOPED HETEROSTRUCTURES.

Spatial localization and diffusion of Si in GaAs and Al sub x Ga sub (1-x) As is investigated using capacitance-voltage measurements and rapid thermal annealing. Si-dopants in delta- doped GaAs and Al sub x Ga sub (1-x) As are shown to be localized on the length-scale of the lattice constant, if the epitaxial layers are grown at low substrate temperatures. The previously unknown diffusion coefficients of Si in GaAs and Al sub x G sub (1-x) As are determined. The delta-doping technique is applied to selectively doped heterostructures for high electron mobilities. It is shown that highest electron-mobilities can be achieved, if the doping-profile is delta-function-like, due to a minimization of random potential fluctuations of ionized dopants.