538 Journal of Crystal Growth 71 (1985) 538-550 North-Holland, Amsterdam THE GROWTH OF GaSb UNDER MICROGRAVITY CONDITIONS E. LENDVAY, M. HA,RSY, T. G()R()G, I. GYUR0, I. POZSGAI and F. KOLTAI Research Institute for Technical Physics. Hungarian Acadern~, of Sciences. Budapest. Hungary J. GYULAI, T. LOHNER, G. MEZEY, E. KOTAI and F. P,A, SZTI Central Research Institute for Physics. Hungarian Academy of Sciences, Budapest, Hungary and V.T. HRJAPOV, N.A. KULTCHISKY and L.L. REGEL Research Institute for Cosmic Investigations. Moscow. USSR Received 5 April 1984; Manuscript received in final form 4 March 1985 A high quality GaSb bicrystal was grown in a Bridgman type arrangement under microgravity conditions on board of Salyut-6. Rutherford back-scattering measurements indicate oxide and damage free surfaces. Scanning Electron Microscopy revealed micro- facets on the space grown sample. The morphology of the sample suggests a crystallization quite free of a wall effect. A comparison is given between space and terrestrial GaSb ingots, showing differences in surface quality, crystal perfection and hole mobilities. In the space grown sample a l% ~ 2700 cm2 v-1 s-1 value was found while for the terrestrial control this value was only 2000 cm2 v-1 s-1 1. Introduction Binary Am B v compounds are important materi- als for optoelectric applications. To date lasers, detectors and solar cells have been fabricated using these semiconductors. GaSb, with a direct band gap of 0.74 eV, is a very attractive material for optoelectronic devices. Under conditions currently used for growth it has a p-type conductivity without intentional doping. However, bipolar conductivity can also be achieved using different dopants, such as Sn, Te or Zn [1-4]. More recently the develop- ment of very high quantum efficiency GaSb pho- todetectors in the 1.3-1.7 nm region have been reported [3-5]. GaSb substrates are also used for A1GaSb, GaAsSb, InGaAsSb and GaA1AsSb de- tectors, LEDs and laser devices. For these applications damage and inhomo- geneity free crystals of high quality with low dislo- cation densities are needed. Numerous publica- tions describing different growth methods and aimed to improve the quality of GaSb crystals have been recently published, but the obtained materials often contain macroscopic and micro- scopic defects. Twins, for instance, can be easily formed and also microfaceted growth is frequently observed [6,7].GaSb is an ideal model for space technology. Among the semiconductors it has a relatively low melting point. Growing crystals un- der microgravity conditions is not an energy con- suming process. Investigating the GaSb crystals grown both the macroscopic and microscopic growth mechanisms could be studied examining the crystal (defect) structure and morphology, as well as the semiconductor properties. Microscopic inhomogeneities associated with changes in the growth rate respond very sensitively to the convec- tion and the mechanical vibrations of the growth system [8,9]. In order to study these effects in detail, GaSb growth experiments were performed during the first Soviet-Hungarian Space Flight on board of Salyut-6, under microgravity conditions, 0022-0248/85/$03.30 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)