MOVPE growth and characterisation of ZnTe epilayers on (1 0 0)ZnTe:P substrates

Abstract

The growth of ZnTe by atmospheric pressure metalorganic vapour phase epitaxy on (1 0 0)ZnTe:P substrates is reported. The epilayers were grown at 340°C after in situ H 2 heat cleaning of the substrate for surface oxide removal. Secondary ion mass spectrometry analysis of as-grown samples has shown that in situ treatment temperatures above 240°C are necessary. Moreover, no phosphorous incorporation occurs in the epilayers by either diffusion from the substrate or auto-doping through the vapour. Carbon is instead incorporated in the epilayers at concentrations higher than in the substrate. 4.2 K photoluminescence (PL) measurements show a dominant band edge emission, whose main component at 2.3809 eV is identified, by comparison with reflectance spectra, with the 1s-state free exciton line, its FWHM being 2.2 meV. A weak 2s-state exciton line also appears on the high-energy side of the ground-state emission, further confirming the high optical quality and purity of the epilayers. Donor and acceptor bound exciton lines are also identified within the band edge region, whilst free-to-bound and donor–acceptor pair bands below 2.37 eV in the PL spectra are ascribed to luminescence from the substrate.