Molecular beam epitaxial growth of high-reflectivity and broad-bandwidth ZnTe/GaSb distributed Bragg reflectors

Abstract

This paper reports the molecular beam epitaxial growth and characterization of high-reflectivity and broad-bandwidth distributed Bragg reflectors (DBRs) made of ZnTe/GaSb quarter-wavelength (k/4) layers for optoelectronic applications in the midwave infrared spectral range (2-5 lm). A series of ZnTe/GaSb DBRs has been successfully grown on GaSb (001) substrates using molecular beam epitaxy (MBE). During the MBE growth, a temperature ramp was applied to the initial growth of GaSb layers on ZnTe to protect the ZnTe underneath from damage due to thermal evaporation. Post-growth characterization using high-resolution x-ray diffraction, atomic force microscopy, and transmission electron microscopy reveals smooth surface morphology, low defect density, and coherent interfaces. Reflectance spectroscopy results show that a DBR sample of seven k/4 pairs has a peak reflectance as high as 99.0% centered at 2.56 lm with a bandwidth of 517 nm.