Abstract
A technique has been developed which unambiguously distinguishes between interfacial and bulk transport. The technique resembles a time-of-flight measurement, but utilizes a higher degree of time-resolution to separate carrier movement in the interfacial region from bulk effects. The injection rate is extremely sensitive to the condition of the interface between Al and ultrapure, high resistivity CdS or CdSe, for which ordinary I–V and C–V characterizations are impossible. When the interface is constructed quickly on single crystals cleaved in UHV, the injection approaches the theoretical maximum rate, the trap-free space-charge-limited current. However, when metal deposition is interrupted at submonolayer coverages, and exposed to UV light, the eventual thick Al electrode forms an altered contact on CdSe. This contact displays an order of magnitude smaller injection rate and is unstable at high field. The larger effective barrier is attributed to a thicker reacted Al layer, whose formation is enhanced by increased bond breaking due to the excess photogenerated carriers.
Published Version
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