Chu Junhao

Infrared absorption in In-doped degenerate Hg1−xCdxTe

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.

Photoluminescence study on Hg1-xCdxTe thin film implanted with As ion

Photoluminescence spectra of a series of MBE-grown Hg1-xCdxTe samples with the same mole fraction of about x ≈0.39 have been measured at different temperatures from 5 to 100 K. By aid of the temperature and exciting laser power dependence of photoluminescence peak energy and relative intensity, as well as of the comparison with other measurements, four main structures dominating in the photoluminescence spectra are attributed to band to band, DoX, AoX and DoAo transitions. A deep donor state level located at about 8.5 meV below the bottom of the conduction band has been observed and is determined to be due to the arsenic-occupied mercury vacancies. Two acceptor levels located at about 14.5 meV and about 31.5 meV above the top of the valance band have also been found from the measuements, which are identified as the mercury vacancies and As in anion site, respectively.