Laser-induced selected area epitaxy of CdTe and HgTe

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Abstract
The enhancement of growth rate of epitaxial CdTe on GaAs(100)2°→(110) substrates is investigated. Photolytic decomposition of the precursors dimethylcadmium with either dimethyl telluride or diethyl telluride is brought about by absorption of 257 nm radiation from an intra cavity doubled argon ion laser. Growth rate was studied as a function of ultraviolet (UV) intensity by the time resolved reflectivity method to monitor CdTe film thickness. Evidence for enhancement of growth rate from surface absorption of uv radiation is discussed together with the factors that can affect pattern definition. The photoenhancement factor depends primarily on the ratio of photolytic to pyrolytic growth rates, the more stable dimethyl telluride yielding higher photoenhancement factors than diethyl telluride. Results on photopatterned bar and mesa structures are presented with feature sizes down to 50 μm. Preliminary experiments on HgTe photopatterning indicate similar kinetic mechanisms to those for CdTe but slow desorption of reaction products might be responsible for lower growth rates. Possible surface reaction mechanisms are discussed and the prospects for selected area epitaxy of mercury cadmium telluride (MCT) considered.

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