The Variation of Surface Leakage Current after Thermal Treatment for CdTe

Abstract

After CdTe wafers are polished mechanically and chemically, wider, narrower bands are observed at 1.4 and 1.54 eV by photoluminescence (PL), respectively. The samples are annealed in a vacuum evaporator before depositing the electrode. Thermal annealing depending on time duration and temperature shows a change of the ratio of I/I(A 0 , X) (intensity ratio of the bands to that of emission from excitons trapped by neutral acceptons). The PL intensity ratio of these bands is reduced by optimum annealing conditions. Raman scattering and I-V characteristics are also measured.Introduction CdTe compound semiconductor is recognized as the promising material for X-ray and g-ray detectors operating at room temperature. It is known that the charge collection efficiency of the detectors can be improved by applying a high bias voltage, but the large leakage current of a CdTe detector in MSM (metal-.semiconductor-.metal) configuration limits its operating voltage. It usually has been attempted to suppress the leakage current by making the detectors as Schottky structure. Since the surface layer plays an important role in interface properties, thermal treatments [1] are carried out in vacuum with different time durations and temperatures before depositing indium electrode to form the Schottky contact. Surface layers have been studied using Raman scattering, photoluminescence (PL) and I-V measurements.