ABSTRACT
We have compared photoluminescence (PL) and reflectivity spectra of MBE-grown undoped, Cl-doped, and N-doped ZnSe. Free exciton peak intensity gradually increases with increasing temperature with respect to bound exciton and its energy agrees well with reflectivity below 100 K. At higher temperatures PL peak energies were close to or a few meV below their reflectivity signatures. This probably indicates that the photoluminescence peak is originated either from free exciton or a combination of free exciton and donor-to-free hole (DF), depending upon the temperature regime. We also observe the photoluminescence associated with the first excited excitonic state, whose relative intensity with respect to that of ground state increases with increasing temperature. The temperature dependence of the bandgap m ZnSSe or ZnMgSSe is found to be identical to that of ZnSe within an experimental error. In the micro-Raman study of ZnSe, ZnSSe, ZnMgSe, and ZnMgSSe, we observe a plasm on-phonon coupling mode as well as their characteristic longitudinal optical phonons. Its intensity is usually stronger for p- or n-type GaAs than for semi-insulating one, as expected.
