A Raman spectroscopy study of MBE-grown Hg _{1− x} Cd _x Se alloys grown on GaSb (2 1 1) by molecular beam epitaxy

This work presents a Raman spectroscopy study of Hg _{1− x} Cd _x Se alloys grown on GaSb (2 1 1) substrates by molecular beam epitaxy. For the Raman spectra of Hg _{1− x} Cd _x Se (0 ≤ x ≤ 0.6) measured with low laser excitation intensity, no sample damage is observed and the Raman spectra are dominated by the HgSe-like phonon modes. However, with a higher laser excitation intensity, material damage in the form of void formation is observed due to Hg loss and the resultant Raman spectra are dominated by CdSe-like phonon modes. For a constant laser excitation intensity the material damage was found to increase with increasing Cd content due to weakening of the Hg-Se bond in the presence of Cd. A separate Raman study undertaken on the cross-section of a compositionally graded HgCdSe sample clearly indicates that the integrated Raman intensity exhibits an essentially linear dependence on Cd content for the composition range, 0.30 ≤ x ≤ 0.45. The results of this study provide a useful guide for the development of any thermal procedure to be used in any detector fabrication process, as well as indicating that Raman spectroscopy has the potential to be developed into a general purpose tool capable of assessing HgCdSe compositional uniformity.