Spectroscopic investigations of CdS at high pressure

The photoluminescence spectrum and absorption spectrum as well as resonant Raman scattering tuned by pressure in heavily doped CdS have been studied. The pressure coefficients of shallow levels (I₂ and I₁) and deep levels (G₅ and R) are measured. A new optical-absorption method under pressure was developed and the shift of band gap with pressure of CdS in the direct-band-gap wurtzite phase and indirect-band-gap rock-salt phase was measured. From the experimental results of resonant Raman scattering tuned by pressure we conclude that at about 27 kbar CdS undergoes a complete phase transition from the wurtzite phase to the rock-salt phase. After the phase transition there is no two-phase mixture, and the material still has semiconductor characteristics.