Evaporated and Recrystallized CdS Layers

Heat treatments of evaporated CdS layers in nitrogen containing HCl and traces of oxygen, and providing a transport of CdS and copper are reported. Recrystallization of areas up to several mm2 are observed. At 25°C, the treated layers show mobilities of 140 to 230 cm2/V·sec, photoconductivities of 10−3 to 2×10−1Ω−1cm−1 at 750 ft-c (2600°K white light) with light-to-dark-current ratios of 108–109 and response time (decay) of 300 μsec to 1.2 msec at 100 ft-c. The level distribution and capture cross section for electrons is investigated using spectral distribution, light intensity, and temperature dependence of photoconductivity, thermally stimulated current and response time analyses. Levels at 0.23, 0.43, 0.67, 1.05, and 2.05 eV are observed and the latter three attributed to Cu centers. Compared to other layers and single crystals, these layers show a density of