Accession Number : ADA332796
Title : Study of the Growth, by Solid State Recrystallization, and Assessment of ZnSe Crystals as Substrates for Blue Emitting Devices.
Descriptive Note : Final rept.
Corporate Author : EUROPEAN RESEARCH OFFICE LONDON (UNITED KINGDOM)
Personal Author(s) : Triboulet, Robert
PDF Url : ADA332796
Report Date : NOV 1997
Pagination or Media Count : 17
Abstract : For a better understanding and control, the process of solid state recrystallization of ZnSe is studied through the different aspects of growth kinetics, influence of residual impurities on the kinetics, initial texture/orientation of the growing crystals' relationship, twinning issue, determination of the vacancy concentration, and doping. An activation energy of tilde 400 kJ/mole is determined for the migration of the grain boundaries at the early stage of the growth under both Zn- and Se-rich conditions. Like in the case of metals, a law of the form D = kt(1/n) is found between the grain diameter D and the time t, 1/n being respectively about 0.25 and 0.1 under Se-rich and Zn-rich conditions. The presence in the source of residual donors such as A1, In and C1 is found to inhibit the SSR grain growth. Preferential orientations (111), (311) and (220) found by X-ray diffraction in the initial CVD samples are progressively left, and growth directions around (110) are found to be favored. The presence of twins in most of the initial micrograins, as found from electron microscopy observations, is supposed at the origin of twinning frequently observed in the crystals. The size and quality of the SSR crystals are found to depend on orientation and size factors of the initial samples. The dislocation density of the SSR crystals is estimated to be < 102 sq cm. A vacancies concentration of some 10(exp 19) cu cm is estimated on both sides of stoichiometry, assuming a vacancy model to be valid, from lattice parameters measurements. Using A1 diffusion, conductive (8 x 10(exp -2) omega cm) n-type crystals with carrier concentrations up to 5 x 10(exp 17) cu cm and electron mobilities about 200 sq cm/Vs at room temperature are obtained.
Descriptors : *X RAY DIFFRACTION, *KINETICS, *GRAIN GROWTH, *SOLID STATE PHYSICS, *RECRYSTALLIZATION, EMISSION, METALS, SOURCES, ORIENTATION(DIRECTION), CHARGE CARRIERS, GRAIN SIZE, SUBSTRATES, CRYSTALS, IMPURITIES, ROOM TEMPERATURE, ELECTRON MICROSCOPY, DISLOCATIONS, RESIDUALS, ZINC, DOPING, N TYPE SEMICONDUCTORS, BLUE(COLOR), STOICHIOMETRY, GRAIN BOUNDARIES, ELECTRON MOBILITY, ACTIVATION ENERGY.
Subject Categories : Properties of Metals and Alloys
Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE