Dependence of Excitonic Emission Lines and the 1.47 eV Band on Growth Temperature and Substrate Misorientation in MOCVD-Grown CdTe Films on (100) GaAs

Abstract

Epitaxial CdTe layers were grown on nominally (100)-oriented and 3°-off misoriented GaAs substrates at temperatures between 200 and 425°C by low-pressure metalorganic chemical vapour deposition (MOCVD) with the use of precracking (CH3)2Te gas. The excitonic features, at 4.2 K, exhibited a marked dependence not only on the orientation of the GaAs substrate, but also on growth temperature. A neutral-acceptor bound-exciton line with the narrow full width at half maximum of about 0.6 meV, in a layer on a misoriented substrate, is enhanced in intensity with increasing growth temperature. Remarkable spectral changes of the individual broad bands located in the vicinities of 1.47 and 1.42 eV were also found in the layers grown at temperatures between 350 and 400°C, where the 1.47 eV band with a weak LO-phonon coupling strength became predominant. We discuss the origin of the bound-exciton emission lines and the 1.47 eV band in the heteroepitaxial CdTe layers.