Friday, March 28, 2014

Photoconductive Response of Single Crystal Germanium Layers Prepared by the Pyrolytic Decomposition of GeI2

Layers of single crystal germanium have been prepared by pyrolytic decomposition of GeI2 at about 350°C upon single crystal seeds of germanium by J. C. Marinace. The substrate germanium could be removed and the resultant thin layers (5×10-3 cm) studied. The Hall coefficient and resistivity measured on these layers by Dunlap et al. showed that the layers as grown were usually n type and contained about 1016 donors/cm3. These donors are situated at 0.22±0.04 ev below the conduction band. In the work reported here, the photoresponse of such layers at 77°K was found to extend to about 6 μ in substantial agreement with this thermal activation energy. The 0.2ev donors apparently can be annealed out by prolonged heating at 550°C. The layers could also be intentionally doped with standard acceptors such as Al during formation. It was hoped that it would be possible to obtain the incorporation of Au into the layers. For this purpose, layers for which Au doping was attempted were annealed to remove the 0.2ev donors. Although some of the layers became p type, a comparison of the photoresponse at 77°K with the photoresponse obtained for a 5×10-3 cm thick ptype plate of regularly Audoped germanium showed no evidence for the 0.15 ev Au level. Likewise, annealed layers for which Ag doping was attempted were examined but yielded no positive identification of the 0.14ev level of Ag.

Source:IEEE

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