Electrical and optical properties of Au in cadmium telluride

Abstract

Gold diffused CdTe crystals have been studied by electrical and optical measurements, involving admittance spectroscopy, low temperature photoluminescence excited with a tunable dye laser, absorption, and magneto-optical measurements. It has been shown that Au introduces an acceptor level at 263 meV above the valence band. Its properties can be understood in terms of classical deep acceptor-like states with a d10 impurity core. Substitutional acceptor Au concentrations up to ∼5×1016 cm−3 could be obtained with a two-step diffusion process. Otherwise, simple diffusions at temperatures higher than 600 °C lead to the formation of complex centers. Some complex-bound exciton lines have been identified. They have been tentatively attributed to neutral substitutional-interstitial associates. Magneto-optical studies have shown that the acceptor Au bound exciton ground state was a J=1/2 state, and have confirmed that Au acceptor was indeed on Cd site in a Td symmetry. The diamagnetic shift of the neutral acceptor bound exciton complex is well explained in terms of the pseudo-donor model. Also the cubic crystal field effects have been found to be very important.