Structural aspects of MOCVD-grown Hg1−xCdxTe layers on novel GaAs substrates

Abstract

X-ray diffraction studies of six samples of metal organic chemical vapour deposition (MOCVD)grown Hgl_xCdxTe on novel GaAs substrates have been carried out. The six GaAs substrates have (311), (~ii), (511), (51f), (711) and (711) orientations. The absolute polarities of the six substrates, initially unknown, have been determined by X-ray anomalous scattering (after the layers were deposited). The orientations and absolute polarities of the six Hg~_xCdxTe layers have similarly been determined and follow the substrates. An extensive set of integrated-intensity data has been collected from the (311) Hg~_xCdxTe layer, which is of the order of 1 Ixm in thickness. Least-squares analysis of these data yields information about the thermal vibrations of the atomic species, extinction effects and the average composition of the Hg~_xCdxTe layer. Some results of double-crystal rocking-curve measurements for each of the six samples are also reported. The Rutherford backscattering of 2 MeV He ions has been used to determine independently the absolute polarity, composition and quality of the (311) and (311) Hg~_xCd,,Te layers. ExperimentalThe MCT layers were grown in an MR Semicon Quantax 226 MOCVD reactor. The (2 in) GaAs substrates, supplied by Wacker-Chemitronic GMBH, Germany, were polished on both sides and of nominal (311), (511) and (711) orientations. The substrates were halved and one half was inverted in the reactor prior to deposition of the MCT la_yers, i.e. MCT layers were grown on (n 11) and (~11) GaAs substrates placed side by side in the reactor, for n = 3, 5 and 7