Characterization of laser deposited CdTe and Hg 1− xCd xTe thin films

Abstract

CdTe and Hg 1− x Cd x Te narrow-gap semiconductor materials were deposited as thin films on optical glass, by the laser-assisted physical vapor deposition (LAPVD) process. A pulsed CO 2-TEA laser was used to vaporize the studied materials in a vacuum chamber. The Fourier analysis of the (111) CdTe X-ray diffraction profile was used to determine the average effective crystallite size, the root mean square of the microstrain, the stacking fault probability within the crystallites and the dislocation density for CdTe films of various thicknesses. The X-ray diffraction pattern of the Hg 1− x Cd x Te films contains (100) reflection, indicating highly textured films with [100] direction of the HgTe type structure. Photoacoustic (PA) measurements were done to establish the absorption edge of the CdTe and Hg 1− x Cd x Te thin films. The PA spectra were fitted with an exponential function obtaining 1.45 eV absorption threshold photon energy for CdTe films and around 0.3 eV for Hg 1− x Cd x Te, which corresponds to a x = 0.3 alloy fractional composition.