ON POSSIBILITY OF STOICHIOMETRY CONTROL FOR SEMICONDUCTOR A³B⁵ SINGLE CRYSTALS BY A X-RAY DIFFUSE SCATTERING METHOD. Kirill D.Chtcherbatchev and Vladimir T.Bublik, Moscow State Institute of Steel and Alloys, Dept. of Semiconductor Materials & Devices, Box 034, Leninskii pr. 4, 117936 Moscow, Russian Federation

A method of stoichiometry control for low dislocation density (N_d<10⁴cm^-2) A³B⁵ single crystals based on a measurement of a X-ray diffuse scattering (XRDS) by microdefects is proposed. Point defect clusters of various sizes, shapes and nature (for example, dislocation loops, inhomogenities with diffuse boundary, nuclei of metastable and stable phases etc.) can be determined as microdefects (MD). The feature of a stoichiometry composition is a high probability of an annihilation of nonequilibrum interstitials and vacancies in each sublattice without MD formation. Hence the principal criterion of the state is a minimum of XRDS. The formation of MD may proceed in two independent ways. The fist one is the association of point defects which became nonequilibrum during the post-crystallization cooling. The second one is the formation of MD during the decomposition of supersaturated by A or B component solid solution. A contribution of the second process in MD formation increases with increasing of a deviation from stoihiometry. We used the method to control stoihiometry in two systems. The first one is undoped InSb single crystals grown from a melt with various contents of Sb (50, 51 and 52%). And the second one is Te-doped GaSb (n=1.5(13.8(10¹⁷cm^-3). We analyzed both Huang and asymptotic diffuse scattering by microdefects. Using of the latter one proved to be preferable under the conditions of simultaneous presence of MD both of negative (vacancionic) and positive (interstitial) sign of dilatation. This method gave an opportunity to study the MD which were not revealed by TEM and selective etching. We found out that the crystal grown from the melt with 51% at. Sb had the most stoichiometric composition. We also managed to fix a transfer through a pseudobinary section GaSb-Ga₂Te₃ (the sample GaSb(Te) n=13.8(10¹⁷cm^-3). Hence the obtained results can be solid background for creation of highly informative and nondestructive method of stoichiometry control.