Investigation of photons in HgCdTe using Raman scattering and far-infrared reflectivity

Abstract

We have measured and analysed the Raman-scattering and far-infrared spectra from unoriented n-and p-type Hg, -,Cd,Te with x 0.21. Measurements were made in the 80-180 cm" frequency region at temperatures of 10 and 80 K. Comparison of the n-and p-type spectra leads to the conclusion that the electronic contribution to the Raman spectra is small. In particular, the data show that the 135cm" feature originates in lattice effects and may be related to the Te-3Hg-Cd combination as previously suggested. The weak but distinct fine structure present in the CdTe-like reststrahlen band at -153 cm" is tentatively assigned to be a result of localised oscillations of Cd ions in the alloy lattice. A study of the spectral changes between 10 and 80 K clearly indicates a softening of the HgTe-like TO phonon

Structural analysis of the semiconductor-semimetal alloyCd1−xHgxTeby infrare

“…3͒ gives TO frequencies of 121.0 cm Ϫ1 for the HgTe-like vibration and 151.0 and 155.5 cm Ϫ1 for the CdTe-like vibrations, which agree to within 0.5 cm Ϫ1 with other results. 25 The LO frequencies are 139.5 cm Ϫ1 for the HgTe-like vibration, and 153 and 158.5 cm Ϫ1 for the CdTe-like vibrations. In Ref.…”

Raman spectroscopic study of HgCdTe epilayers for infrared detector array fabrication

“…Raman Spectra (RS) on as-grown sample is marked as curve A. In this wafer, prominent Raman peaks are detected at 108 cm À1 , 126 cm À1 , 143 cm À1 and 154 cm À1 [3,10]. These peaks are regarded as a defect mode, TO 2 , LO 2 and un-resolved TO 1 and LO 1 modes respectively.…”

“…for optical phonon frequency at the centre of the Brillouin zone (point of symmetry) in the case of back scattering geometry. On the (1 1 1)B surface of HgCdTe, scattering of the optical phonon at k = 0 behaves like a combination of HgTe-like vibration mode and CdTe-like vibrational mode as explained in the previously [8][9][10]. It therefore follows that the observed red-shift and asymmetrical broadening in the Raman peaks is a manifestation of lattice disorder at the surface of chemically etched MCT2 wafer [6,[14][15][16].…”

“…Raman spectroscopic technique has another advantage of being contactless and nondestructive method. HgTe and CdTe like transverse optical (TO) and longitudinal optical (LO) phonon features were reported using polarization dependent Raman scattering on Hg 0.8 Cd 0.2 Te and Raman scattering is reported to be sensitive to the surface condition [7][8][9][10][11][12][13]. But correlation of the phonon features with the surface condition is not attempted.…”

Model of the two well potential for Hg-atoms in the Hg1 - xCdx Te alloy lattice

“…An additional mode caused by introducing of the hydrogen atoms in the tetrahedra in the crystal lattice of CdTe was observed in the FIR-spectra obtained using synchrotron radiation as the source [11]. The problem of the additional phonon modes (APM) in the 100-115 cm −1 range has existed for the Hg 1− x Cd x Te alloys for the last forty years [13][14][15][16][17][18][19][20][21][22]. The additional mode is observed too in HgTe crystals in this same range [23,24].…”