Interstitial and substitutional Zn in InP and InGaAsP

Closed‐ampoule Zn diffusion in InP results in a net acceptor concentration that is much smaller than the Zn concentration. After subsequent annealing of InP in an atmosphere without Zn, the Zn and net acceptor concentrations have become almost identical, due to a decreased Zn concentration and an increased net acceptor concentration. The annealing treatment gives rise to a decreased contact resistivity. The diffusion depth has not changed. Annealing with a SiN cap on the InP surface does not have this effect on the concentrations. These annealing effects also take place in InGaAsP on InP layers. The results can be explained quantitatively by assuming that Zn is incorporated as both substitutional acceptors and interstitial donors and that only the interstitial Zn is driven out by the annealing, owing to its large diffusion coefficient. Profiles calculated with this interstitial‐substitutional model can be fitted to experimental profiles assuming Zn to diffuse as singly ionized interstitial donors. This mo...