Observation of deep levels in Hg1−xCdxTe with optical modulation spectroscopy

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Abstract
We have applied the technique of optical modulation spectroscopy to the narrow‐gap semiconductor Hg1−xCdxTe. This technique consists of measuring the change ΔIp in the transmitted intensity Ip of a tunable dc probe beam (with photon energy h/ωP<Eg ) due to a fixed‐wavelength chopped pump beam (with photon energy h/ωP≳Eg ). The ΔIp/Ip vs h/ωp spectra were measured for liquid phase epitaxial Hg1−xCdxTe samples at 94 K with x≅0.24–0.37. All spectra show three distinct peaks. The strongest peak occurs near Eg. The other two peaks are relatively sharp and occur below Eg. The energies of these two peaks are close to those of deep levels in Hg1−xCdxTe as recently determined by other techniques. This optical modulation technique, which is relatively simple, contactless, and nondestructive, may have significant potential for high‐sensitivity and high‐resolution study of deep levels in semiconductors.