RAMAN-SCATTERING STUDIES OF DOPING OF EPITAXIAL ZINC SELENIDE

The application of spin-flip Raman scattering spectroscopy to the stud y of doping in semiconductors is discussed, with special attention to the topical problem of the p-type doping of ZnSe, which is a key issue in the development of wide-band-gap optoelectronic devices. Brief int roductions to the theory of spin-flip Raman scattering and to the rele vant experimental techniques are given, followed by a detailed discuss ion of recent results on the spin-flip scattering of ZnSe doped with h igh concentrations of nitrogen. A new spin-flip Raman scattering signa l has been observed in ZnSe:N and is associated with the presence of a new, deep donor center. This new donor is involved in the compensatio n of the nitrogen accepters and its introduction is therefore an undes irable side-effect of nitrogen doping. It appears to be introduced bot h in molecular beam epitaxy (MBE) and in metallo-organic vapor phase e pitaxy (MOVPE). In samples grown by MOVPE, annealing of the sample inc reases the active acceptor concentration but does not affect the signa l due to the deeper donor, suggesting that annealing activates accepto r centers but does not eliminate the compensating donor centers.