Generation of the A-centres at the surface of CdTe(Cl) by YAG:Nd laser radiation

Abstract

A mechanism for formation of a potential barrier at the interface of p-CdTe(Cl)-SiO 2 structure using the second harmonic of a Q-switched YAG:Nd laser radiation (LR) is proposed which involves thermogradient effect (TGE). According to the TGE in CdTe(Cl) the interstitial atoms of Cd (Cd i) move along a temperature gradient, towards increasing temperature, but Cd vacancies (V Cd) and atoms—in the opposite direction, into the bulk of the semiconductor, where temperature is a minimum. Since, the Cl atoms and V Cd are localized in the same place of the semiconductor and have opposite charges they are aggregate as A-centres. Result of investigation of the photoluminescence (PL) spectra at 5 K shows that the concentration of the A-centres is increased owing to aggregation of the V Cd with Cl after laser irradiation. Investigation of the current–voltage characteristic in crossed magnetic field B z=0.3 T showed that at the interface of CdTe(Cl)-SiO 2 a potential barrier arises after irradiation by the YAG:Nd laser at intensity larger than the threshold intensity I th=0.2 MW/cm 2. Investigation of the morphology of an irradiated surface using the Atomic Force Microscope has shown that generation and redistribution of point defects in CdTe(Cl) is possible in solid state at room temperature.