EVAPORATED AND RECRYSTALLIZED CDS LAYERS.
DELAWARE UNIV NEWARK DEPT OF PHYSICS
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Heat treatments of evaporated CdS layers in nitrogen containing HC and traces of oxygen, and providing a transport of CdS and copper are reported. Recrystallization of areas up to several sq mm are observed. At 25C, the treated layers show mobilities of 140 to 230 sq cmVs, photoconductivities of 0.001 to 0.2ohmscm at 750 ft-c 2600K white light with light-to-dark-current ratios of 10 to the 8th power - 10 to the 9th power and response time decay of 300 microsic to 1.2 ms 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 letter three attributed to Cu-centers. Compared to other layers and single crystals, these layers show a density of 10 to the 12th powercu cm of levels attributed to sulfur vacancies in the range between 0.3 and 0.65 eV and a not detectable amount of intrinsic defects acting as quenching centers at 0.9 and 1.35 eV. This is explained by a Cu-enhanced recrystallization in a CdS-supplying atmosphere at temperatures 620 to 650C below the temperatures otherwise used for crystal growth, and thereby efficient annealing of intrinsic defects. Author
- Physical Chemistry
- Fabrication Metallurgy
- Miscellaneous Materials