Structural Analysis of InAs1-xSbx Epilayer Considering Occurrence of Crystallographic Tilt Exploiting High-Resolution X-Ray Diffraction

Abstract

InAs1-xSbx epilayer has nonlinearity bandgap energy between 180 and 350 meV according to the relative composition x of Sb at room temperature. For this reason, the wavelengths operating as a photodetector are in the mid-infrared (3-5 mu m) and long-wavelength infrared range (8-12 mu m). Photodetectors of these wavelengths can be used in the fields of pollutant detection, infrared thermal imaging, lidars, or optical countermeasures. Since the bandgap energy of InAs1-xSbx epilayer changes according to the relative composition of Sb, the measurement of InAs1-xSbx epilayer composition is crucial for predicting device characteristics. In this study, high-resolution X-ray diffraction was used to measure the mean composition of specimens without damaging the specimens of InAs1-xSbx epilayer. InAs1-xSbx thin films were grown epitaxially on the GaSb substrate having a similar lattice constant as the thin films by utilizing the molecular beam epitaxy method at various growth temperature conditions. Here, tilt of the growth direction in InAs1-xSbx thin films was observed despite having no off-cut angle of the GaSb substrate. Cases considering and not considering the tilt of the growth direction were analyzed to show a 3% difference in the relative composition of Sb in InAs1-xSbx thin films. Accordingly, this study revealed that the growth tilt of the epilayer must be taken into account when measuring the precise composition of InAs1-xSbx thin films grown on a GaSb substrate using high-resolution X-ray diffraction.