Photolumineseence in AN-Doped CdS Crystals

Abstract

Single crystals of CdS doped with Al were grown by a sublimation method. Their photo-luminescence properties were measured and experimental results were discussed by comparing them with those of undoped crystals. Besides the usual edge emission line of 517.0 nm, a newemission line of 523.7 nm was observed at 4.2K. The peak wavelength of this emission shifted to shorter wavelengths as the excitation intensity increased. It was a distinctive feature of adonor-acceptor pair emission. This emission is considered to have been caused by an acceptor with an energy of about 0.2 eV above the valence band. The red luminescence which had been observed in several undoped crystals was also observedin all Al-doped crystals. The emission spectrum has a Gaussian distribution with the peak a 750 nm at 77 K. The peak wavelength of this emission shifted to shorter wavelengths as the temperature rose. The complex center with an Al donor and a Cd vacancy seems to have been responsible for this emission analogous to the luminescence characteristics with the self-activated emission in ZnS.