Photostimulated changes of electrical characteristics of Ag/CdTe thin film structures

Abstract

Electrical, optical and structural properties of Ag/CdTe structures exposed to thermal (in dark) and photoannealing (under illumination) have been studied. The effective diffusion coefficient of Ag in CdTe films have been estimated from resistance versus duration of annealing curves. In the range of 280-420 degrees C the effective coefficient of thermal diffusion (D-t) and photodiffusion (D-ph) are described as D-t= 1.9x10(5) exp (-1.60/kT) and Doh =8.7x 10(3) exp(-1.36/kT). The acceleration of Ag diffusion under illumination was tentatively attributed to photoionization of Ag increasing the interstitial flux of silver. Ag/CdTe structures exposed to annealing were characterized by X-ray diffraction (XRD), I-V, CV, conductivity- temperature and optical transmission measurements. In XRD patterns of annealed Ag/CdTe structures, besides the intensive (111) peak of cubic CdTe, the weak peaks of Ag-2 Te phase are also present. The temperature dependence of conductivity of annealed Ag/CdTe structures showed the energy levels 0.13 eV.