FORMATION OF SUBBANDS IN DELTA-DOPED SEMICONDUCTORS

The formation of the two-dimensional subbands in uncompensated delta-doped semiconductors from single impurity bound states with increasing impurity concentration is calculated using multiple-scattering theory. Previous calculations treated the delta plane as a metallic sheet by solving a one-dimensional Schrodinger equation in a self-consistently screened one-dimensional potential and could not reproduce single impurity bound states in the limit c --> 0. In contrast to this approximation multiple-scattering theory can describe well both limits of small and large c. The crossover from impurity bands at low concentrations to subbands at large concentrations is discussed and a Mott transition within the delta plane (defined as the vanishing of the gaps in the density of states) is found at c(cr) = 9.95 X 10(10) cm-2 in the case of GaAs:Si.