DLTS Study on the Gradation of the Trap Concentration Profiles in n-CdTe Crystals

DLTS measurements were carried out on three types of metal/n-CdTe junction: I. gold evaporated on an etched surface; II. gold evaporated on a cleaved surface; III. cadmium evaporated on a cleaved surface. Type I had a tellurium-rich layer and type III a cadmium-rich layer. The concentration of level E4(energy depthEC-ET=0.33 eV), one of the six electron traps detected in this experiment, decreased rapidly near the interface in type I at room temperature, but increased in type III. A relationship was found to exist between level E4and the non-stoichiometric layers. A model in which the gradation of this level's concentration was caused by the diffusion of defects, is proposed, and the diffusion coefficient is estimated to be about 10-17cm2·s-1from the concentration profiles of level E4.