Bulk growth of compositionauy homogeneous III-V ternary anoys

Abstract

Substrates of ternary compound semiconductors such as GaInSb, GaInAs, InPAs, GaInP, etc. are of particular interest for electronic and optoelectronic devices. The main technical challenge in growing bulk crystals of ternary alloys is mechanical cracking of crystals due to spatial compositional inhomogeneity [ 1-41. Cracking can be eliminated by ensuring radial compositional uniformity in the crystals. A planar melt-solid interface shape during growth is necessary in maintaining radial composition uniformity. Due to inherent alloy segregation dictated by the pseudo-binary phase diagrams, the growth interface shift towards the lower temperatures. Hence if the external temperature gradient imposed by the furnace remains constant, the growth interface shape can change from convex to concave during growth. Temperature gradient and growth rate manupulation, proper melt mixing using forced convection have been found to be effective in maintaining radial homogeneity [5]. Furthermore, if the alloy composition in the melt is kept at a constant composition level, the growth interface will automatically remain flat, convex or concave depending on its initial shape. Solute feeding via double crucible technique has been attempted by previous researchers to grow uniform crystals [3,4]. However, double crucible method is suitable only for dilute alloy compositions due to technical difficulties. In this paper, we have described a self-solute feeding method wherein homogeneous ternary crystals of any desired composition could be grown by taking advantage of the fundamental solute diffusion properties in the melt [6].