Investigation of structural and optical characteristics of low temperature nucleated thick ZnTe epitaxy on GaAs (211) substrates by MBE

This paper discusses the growth, structural, and optical investigation of ZnTe epitaxial layer grown on GaAs (211) substrate at different growth temperatures (350 °C, 380 °C, and 410 °C) by Molecular beam epitaxy (MBE) with thickness ∼5–6 μm. The low-temperature nucleation and annealing is carried out to preserve the epitaxial nature of the ZnTe layer on high lattice mismatched GaAs substrate. Structural and optical parameters of the layers are evaluated using High resolution X-ray diffraction (HRXRD) and photoluminescence spectroscopy. The typical HRXRD FWHM of ZnTe layers grown at 350 °C, 380 °C, and 410 °C was 160, 140 and 125 arcsec, respectively. The surface roughness was determined using Atomic Force Microscopy (AFM). The increase in surface roughness of the films was observed at higher temperatures with the appearance of triangular shape features. It is due to facet formation on (111) planes during the ZnTe growth. The combined effect of lateral and vertical features of the ZnTe layer is revealed by Power Spectral Density (PSD) analysis, indicating the epitaxial layer's evolution mode. The scaling exponent of PSD >1 shows that the non-linear effects arising due to reduced sticking coefficient and surface diffusion are more prevalent at higher growth temperatures. Further, the layers were analyzed using variable temperature PL measurements. The PL spectra suggested that the defect states (red emission) in the epilayer reduce with the increase in the growth temperature. •The MBE grown (211) ZnTe epitaxial layers on GaAs substrates were grown at different substrate temperature.•Due to large lattice mismatch between ZnTe epilayer and GaAs substrate, the ZnTe growth was initiated at low-temperature to provide nucleation site.•This study incorporates the different steps of annealing to annihilate the defect density in large lattice mismatch MBE grown (211) ZnTe epitaxial layers on GaAs substrates. There are less reports for annealing of MBE grown ZnTe epitaxial layers.•The tilt angle was measured using HRXRD and incorporated in the revised manuscript and the value is in close agreement with reported values.•The growth conditions were optimized to obtain ZnTe layer crystal quality ∼140 arcsec and surface roughness ∼15 nm.•The evolution of surface roughness with the growth temperature of ZnTe epilayers have been studied using powers spectral density analysis.•The variable temperature photoluminescence was used to observe the band edge peak shift and spectro