Characteristics Of OMVPE-Grown CdTe And HgCdTe On GaAs

Abstract

CdTe layers grown on GaAs have been characterized by photoluminescence measurements (PL), transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS). PL spec-tra of layers less than about 1.1 μm show a shift to lower energy of the exciton band, which we attribute to the compressive strain in CdTe along the CdTe-GaAs interface. Layers thicker than 1.1 μm gave PL indicative of high quality layers of bulk CdTe. TEM studies have shown that the lattice mismatch is accommodated by misfit dislocations at the interface and some by lattice strain. As the layer grows thicker this strain is relieved by dislocation lines in the first micron of the layer. SIMS measurements on these layers indicate negligible Ga diffusion, confirming our earlier findings. High quality mercury cadmium telluride (MCT) layers have been grown on these CdTe buffers, with properties similar to layers grown on bulk CdTe substrates. Double crystal X-ray rocking curves of the best MCT layer grown on GaAs substrates show a full width at half maximum (FWHM) of about 110 arc seconds. The best FWHM obtained on MCT layers grown on CdTe substrates was 125 arc secs.