Pulsed Laser Processing of CdTe and Other II-VI Compound Semiconductor/Metal Interfaces

摘要

We demonstrate that the chemical and electronic properties of the metal/cadmium telluride or other II-VI compound semiconductor are closely related and that atomic-scale processing techniques can be useful in controlling both the metallurgical and the Schottky barrier features of the interface. Pulsed laser processing combined with surface science techniques revealed microscopic chemical interactions at elevated temperatures for representative metal-semiconductor junctions. Optical spectroscopy techniques showed that such chemical interactions produced changes in the deep electronic levels within the semiconductor band gap. Carefully controlled measurements of both chemistry and electronics under UHV conditions established that the E(f) stabilization within the semiconductor band gap was dominated by the presence of these deep levels. Essentially, these deep levels are the link between interface chemistry and Schottky barrier formation. By suppressing this chemical interaction, we were able to control the semiconductor band bending over a much wider range than hitherto possible, achieving the lowest p-type barriers to nondegenerately-doped CdTe reported to date. We have now extended these studies to higher quality CdTe films grown by molecular beam epitaxy. These results offer several new opportunities for further improving the chemical and electrical stability, as well as the absolute Schottky barrier heights of metal contacts to CdTe and other II-VI compound semiconductors. (AW)