Optical properties and disorder of HgCdTe films grown by molecular beam epitaxy

The subject of the study is epitaxial films of Hg1-x 1 - x CdxTe x Te solid solutions with the mole fraction of CdTe, x , varying from 0.3 to 0.7, grown by molecular beam epitaxy, and intended for the manufacture of photodetecting and laser structures operating in the infrared range. The aim of the study is to determine the relationship between the optical and microscopic properties of Hg1-xCdxTe 1 - x Cd x Te solid solutions with fluctuations in their composition. The methods include optical transmission, photoluminescence, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Main results. By comparing the results of optical, structural, and microscopic studies, it is shown that, for the films with x : 0.3, the research data on optical properties make it possible to adequately estimate the bandgap and determine the chemical composition of the material. The high perfection of this material is shown, and it is confirmed that its disorder is caused only by the specifics of the formation of semiconductor solid solutions. For the films with x : 0.7, it is established that data on the bandgap and composition can only be obtained from ellipsometric studies and measurements of optical transmission, whereas photoluminescence spectra at temperatures up to room temperature are formed by optical transitions involving carriers localized on large-scale composition fluctuations. In the films with x : 0.7, the presence of uncontrolled acceptor states is also detected, which may indicate the need to optimize the technology of this material. Practical significance. The limits of applicability of photoluminescence studies for characterizing the properties of solid solutions are identified. The need for further optimization of the technology of materials with large (x x : 0.7) compositions is shown. (c) 2024 Optica Publishing Group