LOWERING OF BAND-GAP ENERGY IN HEAVILY NITROGEN-DOPED ZNSE

This article reports the notable effect of N doping in ZnSe on the ban d-gap energy. The free exciton energy in the epilayers with different N-A - N-D was measured by means of reflectance and photoreflectance sp ectroscopies. The temperature dependence of reflectance, photoreflecta nce and photoluminescence spectra of ZnSe:N epilayers was investigated in detail. It is found that the free exciton energy shifts to low ene rgy side with increasing N concentration, indicating the shrinkage of the band-gap energy due to N doping. The peak positions of near-band-e dge emissions shift to low energy side due to the shrinkage of energy gap. The lattice constant and the strain in N-doped ZnSe were measured by means of X-ray diffraction (XRD). The origins for the shrinkage of energy gap are discussed on the basis of the optical and XRD results.