Infrared absorption in In-doped degenerate Hg1−xCdxTe |
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Authors: | Qian Dingrong Tang Wenguo Shen Jie Chu Junhao Zheng Guozhen |
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Institution: | Shanghai Institute of Technical Physics, Academia Sinica, Shanghai, China |
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Abstract: | The infrared absorption spectra, including absorption edge spectra and below-gap absorption spectra, were investigated both experimentally and theoretically for an In-doped degenerate HgCdTe sample with an electron concentration Ne = 7.0 × 1017 cm-3 for wavelengths 7 μm<L<17 μm at the temperatures 77 K <T< 300 K. The possibility of applying free-carrier absorption theory developed for InSb to HgCdTe is discussed. It is concluded that the virtual crystal approximation works fairly well for HgCdTe and that the two-mode Callen effective charge should be used in the calculation of free-carrier absorption coefficients to account for the two-mode character of the optical phonons of HgCdTe. Good agreement between theory and experiment in the below-gap absorption spectra was obtained. The concentration of ionized impurities was found to be Nimp=3.4 × 1018 cm-3. A good account of the behaviour of absorption edge in the light of Burstein-Moss effect has also been given. |
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