Some aspects of A III B V and A II B VI growth
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Some aspects of AIIIBV and AIIBVI growth Oleg Rabinovich National University of Science and Technology “Moscow Institute of Steel and Alloys”, P.O. Box 409, Moscow, 119313, Russian Federation. ABSTRACT Nanoisland films have been grown via incongruent evaporation films. The basis of incongruent evaporation growth method was worked out. Samples surface morphology has been studied by atomic force microscopy. The surface density and characteristic dimensions of the islands have been shown. INTRODUCTION Heterostructures containing quantum wells based on compound semiconductors and their solid solutions are interesting for application in quantum, optical, and integrated electronics (high efficient light - emitting diodes, lasers, and photodetectors operating in the IR and visible spectral regions). Such heterostructures are commonly grown by molecular beam epitaxy, metalorganic chemical vapor deposition and atomic layer epitaxy. These growth methods require rather expensive apparatus for producing high quality heterostructures. Each technique has its own physicochemical features, which limits its utility in the fabrication of quantum size structures. In particular, molecular beam epitaxy has limitations on the films growth based on intermediate phases in systems with high vapor pressure and incongruent vaporization. In such systems as AIIBVI, AIVBVI and AIIIBV, there is a number of compound semiconductors which display unique properties set. That is why new method incongruent evaporation technique is suggested. This method is unified for using with major part of materials. THEORY
Consider briefly the physicochemical aspects of the applicability of incongruent evaporation to the fabrication island film structures. Let the compound AxB1-x have a homogeneity range, Ȗ. The line V(GKF) represents the variation in vapor composition along the three phase equilibrium line SȺȼLV which is shown in figure 1.
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Figure 1. Sample of phase diagram Ga–Sb Let a homogeneous film of thickness h and density df be deposited onto a substrate. The substrate is nonreactive with the film material, has low vapor pressure, and is wetted by the melt in the temperature range in question. The overall composition and pressure of the saturated vapor in equilibrium with the film at temperature t1 are ɯV and ps, respectively. Vaporization of the film at temperature t1 will shift the overall composition, x, of the mixed phase film along the tie line MN from xL to xȖ because xV > xL [1]. It can be shown that the overall composition of the film at any instant in time is given by:
x (t ) =
M 0 xL − GtSxV
(1)
M 0 − GtS
where Ɇ0 = df Sh is the initial weight of the film, G is the evaporation rate, and S is the evaporation surface area. Thus, vaporization will shift the phase state of the film to the two phase region Ȗ + L, creating conditions for the formation and growth of crystalline nuclei of composition xȖ. Primary nuclei will attach to the film/substrate interface of the parent structure because the work needed for heterogeneous nucleation is les
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