Direct evidence for the trigonal symmetry of shallow phosphorus acceptors in ZnSe - art. no. 205206

Spin-flip Raman scattering has been used to provide direct experimental evi dence that shallow phosphorus acceptors in relaxed ZnSe epitaxial layers gr own on GaAs lie at sites of predominantly trigonal local symmetry. As a con sequence, the energy of the heavy-hole bound exciton is about 0.45 meV less than that of the light exciton. This splitting is significantly smaller th an (and of opposite sign and different symmetry to) the valence-band splitt ing of 3 meV observed due to the macroscopic biaxial tensile strain in the same specimens, The behavior is in complete contrast to that of nitrogen ac ceptors, for which no trigonal field is observed. The experiments provide c onfirmation of the behavior predicted by previous pseudopotential total-ene rgy calculations for the shallow acceptor states formed by these two differ ent group-V dopants when substituting at selenium sites.