CELLULAR STRUCTURE IN LEC TERNARY GA1-XINXAS CRYSTALS

Bulk Ga1-xInxAs single crystals with In composition ranging from x = 0 .02 to 0.1 have been grown by the LEC method from melt compositions of 26.3 to 55 mol% In. Due to segregation effects, the In content in the melt increases during growth. Crystals grown from different initial m elt compositions exhibited cellular structure followed by polycrystall inity when the melt composition had reached a unique critical value of In concentration for a particular set of growth conditions. The point at which cellular structure occurs has been evaluated for a variety o f growth parameters. These parameters include initial melt composition s, thermal gradients in the melt, crystal rotation and pull speed. App lying the knowledge of the conditions for the onset of cellular struct ure has maximized the successful growth of single-crystal ternary mate rial and has been instrumental in increasing indium content. The AB an d KOH etches were used to highlight growth striations, view onset of c ellular structure and examine dislocation density. The In composition in the crystal was determined by low-temperature FL, X-ray lattice par ameter measurement, absorption edge position and WDX.