THE INFLUENCE OF CD OVERPRESSURE IN THE MOLECULAR-BEAM EPITAXY OF INSB/CDTE HETEROSTRUCTURES - A COMBINED RAMAN AND INFRARED-SPECTROSCOPY STUDY

CdTe layers were prepared by molecular beam epitaxy on (100) orientated substrates under various growth conditions involving different substrate preparation methods, substrate temperatures, and Cd/Te flux ratios. Using Raman spectroscopy the crystal structure of the substrate and the overlayer as well as the interfacial chemistry are investigated. Our Raman spectra reveal that interfacial layers consisting of In2Te3 and liberated Sb are formed when CdTe is deposited from a single source. While the thickness of the interfacial layers depends on growth temperature, the formation was independent of the substrate preparation. The application of a Cd overpressure during the growth of the CdTe layers effectively suppresses the chemical reaction at the interface and leads to vastly improved interfaces. Using the combination of Raman and infrared spectroscopies thin layers containing a high density of free carriers are found to be present in the top layer of the InSb substrate. © 1989.