Doping and composition profiling in Hg1−xCdxTe by the graded capacitance-voltage method

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Abstract
A capacitance‐voltage (C‐V) technique is established to simultaneously profile both the band gap (i.e., composition or x value) and doping levels in Hg1−xCdxTe material grown by liquid‐phase epitaxy. A photochemical SiO2 passivation/dielectric (PHOTOX©) is used to fabricate metal‐oxide‐semiconductor devices along the surface of taper etched samples to permit measurement as a function of depth into the layer. In this manner, a depth resolution near 200 Å is feasible. Surface state densities generally in the 1010 cm−2 eV−1 range are achieved with the PHOTOX© passivation, making possible analysis by low‐ and/or high‐frequency C‐V methods. Both the x value and doping levels throughout multiple layer samples of changing material type, composition, and doping level are established. Material with band gaps ranging from about 0.1 to 0.3 eV, and doping levels from 3×1015 to 2×1017 cm−3, are examined. The measured composition results on bulk material samples are found to be in good agreement with other methods of anlysis, namely, visible light reflectance, infrared transmittance, and energy dispersive x ray.

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