BERYLLIUM delta-DOPING OF GaAs GROWN BY MOLECULAR-BEAM EPITAXY.

Spatial localization of Be in delta-doped GaAs within few lattice constants (20angstroms) is achieved at low growth temperatures for concentrations N 2D over Be 10 sup (14) cm sup (-2) as indicated by capacitance-voltage profiles and secondary ion mass spectroscopy. At elevated growth temperatures and at high Be-concentrations significant spreading of the dopants occurs and is explained by (i) Fermi-level-pinning induced segregation (ii) repulsive Coulomb interaction of dopants and (iii) diffusion. The highest Be concentration achieved at low growth temperatures exceeds 2 x 10 sup (20) cm sup (-3) and is limited by repulsive dopant interaction. It is shown that the repulsive Coulomb interaction results in a correlated, non-random dopant distribution. The diffusion coefficient of Be in GaAs is determined and is found to be much lower than previously reported.