Electronic Properties of Photoetched CdSe Films
CdSe films were prepared through physical vapour transport on titanium substrates. Their electronic properties were studied at each of four preparation steps, i. e. evaporation, annealing, chemical etching and finally photoetching (PE). To have a direct probe on each process photoluminescence (PL) was employed combined with electronic measurements and secondary ion mass spectrometry (SIMS). At 3 K two distinct donor-acceptor (DA) transitions at 1. 75 eV and 1. 70 eV were found in the PL spectra. These DA transitions which are produced during the evaporation might be associated with group VII and with alkali metal impurities. After each preparation step the DA transitions change their intensities. It is shown that PE of the films leads to a removal of the deep centers, while the 1. 75 eV transition is blue shifted. In contrast with single crystal CdSe the intensity of the PL increases after PE. The results of the PL are consistent with the electronic measurements. They are explained in terms of a previously published model. This investigation shows that PE improves the electronic properties of polycrystalline CdSe films.
KeywordsIllumination Intensity Shallow Donor Titanium Substrate Na2S03 Solution Thin Film CdSe
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