ISOVPE MCT films grown on pure and alloyed CdTe substrates with different crystalline orientations

Abstract

Epitaxial films of Hg 1− x Cd x Te (MCT) with x≅0.2 were grown on CdTe, Cd 0.96Zn 0.04Te and CdTe 0.96Se 0.04 substrates by the isothermal vapor phase epitaxy (ISOVPE) technique with no mercury overpressure. The growth was accomplished in different crystallographic orientations: (1 1 1)Cd, (1 1 1)Te, (1 1 0) and (1 0 0). The structural characterization of substrates and films was performed by X-ray diffraction (Laue technique), surface chemical etching and optical microscopy. Chemical composition analysis was performed by an electronic microprobe in the wavelength dispersive spectroscopic mode and electrical characterization by Hall effect measurements. MCT is an important semiconductor for the manufacture of infrared detectors. The alloyed substrates have a closer lattice match with Hg 1− x Cd x Te. Furthermore, these substrates usually have a lower dislocation density. Both facts determine a lower generation of lineal defects during growth. This fact could produce a larger carrier lifetime and, as a consequence, better electrical properties of devices. On the other hand the surface morphology of ISOVPE MCT epitaxial films only depends on the crystallographic orientation, being independent of the use of pure or alloyed substrates.