DETERMINATION OF THE FUNDAMENTAL AND SPLIT-OFF BAND-GAPS IN ZINCBLENDE CDSE BY PHOTOMODULATION SPECTROSCOPY

We present the results of experimental determination of the fundamental band gap (E(0)) and the spinorbit split-off energy gap (Delta(0)) of zinc-blende CdSe using photomodulation spectroscopy. The single-crystal CdSe film was grown by molecular-beam epitaxy on a (100) GaAs substrate with a ZnTe buffer layer. Photoreflectance (PR) measurements were performed on the sample at various temperatures from 10 K to room temperature. The sharp derivativelike spectral features associated with the interband Gamma(8)(V)-Gamma(6)(C) and Gamma(7)(V)-Gamma(6)(C) transitions in PR spectra allow us to determine the E(0) and E(0)+Delta(0) band-gap energies. We found that zinc-blende CdSe has a fundamental band gap E(0) of 1.661 eV and a spin-orbit split-off gap Delta(0) of 0.42 eV at room temperature (295 K). The fundamental band gap Eo of zinc-blende CdSe has been mapped out as a function of temperature and the Varshni thermal coefficients have been determined for this material. The results yield E(0)(T)=1.766-6.96X10(-4)T(2)/(281+T)eV.