Fermi-level effect and junction carrier concentration effect on p-type dopant distribution in III-V compound superlattices

The pronounced segregation phenomenon in the distribution of p-type dopants Zn and Be in GaAs and related III-V compound heterostructures has been explained quantitatively by treating simultaneously the processes of dopant atom diffusion, segregation, and the effect of heterojunction carrier concentrations on these two aspects. Segregation of a dopant species between two semiconductor heterostructure layers is described by a model incorporating (i) a chemical effect on the neutral species; and (ii) in addition, a Fermi-level effect on the ionized species. The process of Zn and Be diffusion in GaAs and related compounds is governed by the doubly-positively-charged group III element self-interstitials (IIII²⁺), whose thermal equilibrium concentration and hence also the Zn and Be diffusivities exhibit also a Fermi-level dependence, i.e., in proportion to p². A heterojunction is consisting of a space charge region with an electric field, in which the hole concentration is different from those in the bulk layers. This influences the junction region concentrations of IIII²⁺ and of Zn^- or Be^-, which in turn influence the distribution of the ionized acceptor atoms. The overall process involves diffusion and segregation of holes, IIII²⁺, Zn^- or Be^-, and an ionized interstitial acceptor species. The junction electric field also changes with time and position.

Duke Scholars

Author Teh Yu Tan Thomas Lord Department of Mechanical Engineering and Materia ...