Displaced substitutional phosphorus acceptors in zinc selenide

Spin-flip Raman scattering experiments reveal that shallow phosphorus acceptors in ZnSe grown epitaxially on GaAs are subject to a local crystal field of trigonat symmetry. In relaxed layers, the trigonal field dominates the macroscopic biaxial tensile strain field. The trigonal field is also observed in pseudomorphic layers, where the sign of the overall macroscopic biaxial strain is reversed. In both cases, the wavefunction of the hole bound at the acceptor appears to be sufficiently localised for the effects of the macroscopic strain field to be severely reduced. This increased localisation relative to nitrogen acceptors and the appearance of the trigonal field are in excellent agreement with the results of previous total energy pseudopotential calculations, which predict that substitutional phosphorus acceptors should be displaced from selenium sites in 〈111〉 directions.