Dopant diffusion and segregation in semiconductor heterostructures: Part 1. Zn and Be in III-V compound superlattices

chemical effect on the neutral species; and (ii) a Fermi-level effect on the ionized species, because, in addition to the chemical effect, the solubility of the species also has a dependence on the semiconductor Fermi-level position. For Zn and Be in GaAs and related compounds, their diffusion process is governed by the doubly-positively-charged group III element self-interstitials (I²⁺ _III), whose thermal equilibrium concentration, and hence also the diffusivity of Zn and Be, exhibit also a Fermi-level dependence, i.e., in proportion to p². A heterojunction consists of a space-charge region with an electric field, in which the hole concentration is different from those in the bulk of either of the two layers forming the junction. This local hole concentration influences the local concentrations of I²⁺ _III and of Zn^- or Be^-, which in turn influence the distribution of these ionized acceptor atoms. The process involves diffusion and segregation of holes, I²⁺ _III, Zn^-, or Be^-, and an ionized interstitial acceptor species. The junction electric field also changes with time and position. Received: 20 August 1998/Accepted: 23 September 1998