Thermoreflectance spectra and energy band structure of ZnGeP₂ crystals

Abstract

Abstract The thermoreflectance spectra of ZnGeP 2 chalcopyrite crystals have been investigated with polarized light in the spectral region 2.0 to 5.0 eV at 120 and 320 ° K. Three structures (2.46, 2.53, and 2.59 eV at 120 ° K) due to the optical transitions derived from T 15 — T 1 transitions in sphalerite have been observed by 0.4 eV above the fundamental absorption edge. Crystal‐field and spin‐orbit splittings of the valence band were found to be 0.084 and 0.075 eV, respectively. At higher energies eight thermoreflectance peaks strongly dependent on polarization of light were observed. They were attributed to optical transitions derived mainly from transitions responsible for E 1 E 1 + Δ 1 , E 0 and E 2 structures in the optical spectrum of GaP, the closest binary analogue of ZnGeP 2 .