Raman scattering studies of doping of epitaxial zinc selenide

The application of spin-flip Raman scattering spectroscopy to the study of doping in semiconductors is discussed, with special attention to the topical problem of thep-type doping of ZnSe, which is a key issue in the development of wide-band-gap optoelectronic devices. Brief introductions to the theory of spin-flip Raman scattering and to the relevant experimental techniques are given, followed by a detailed discussion of recent results on the spin-flip scattering of ZnSe doped with high concentrations of nitrogen. A new spin-flip Raman scattering signal 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 compensation of the nitrogen acceptors and its introduction is therefore an undesirable side-effect of nitrogen doping. It appears to be introduced both in molecular beam epitaxy (MBE) and in metallo-organic vapor phase epitaxy (MOVPE). In samples grown by MOVPE, annealing of the sample increases the active acceptor concentration but does not affect the signal due to the deeper donor, suggesting that annealing activates acceptor centers but does not eliminate the compensating donor centers.