Crystal-Growth Technology for Ternary III-V Semiconductor Production by Vertical Bridgman and Vertical Gradient Freezing Methods with Accelerated Crucible Rotation Technique

Substrates of III-V ternary compound semiconductors with variable bandgaps orlattice constants still remain very attractive for a variety of electronic, optoelec-tronic, and photovoltaic devices. However, the commercial technology for growinglarge-diameter, compositionally homogeneous, bulk III-V ternary crystals has notbeen fully developed. This chapter discusses the fundamental challenges that haveimpeded the rapid progress of ternary crystal growth. Due to the intrinsic separa-tion between liquidus and solidus in the pseudobinary phase diagrams used forgrowing ternary crystals, alloy segregation is a major issue. This, in turn, leadsto (a) low yield of wafers with the same composition, (b) cracking of crystals dueto constitutional supercooling and strain arising from the compositional grading,and (c) nonhomogeneous wafers due to the curved solid/liquid interface shape.Some of the recent advances made to overcome these challenges for the growthof Al-Ga-In-As-P-Sb-based ternary substrates have been presented. The precisecontrol of heat and mass transport in the melt that is necessary during ternarycrystal growth will be discussed. In particular, the crucial role of melt stirring usingaccelerated crucible rotation technique (ACRT) has been highlighted. The verticalBridgman (VB) or vertical gradient freezing (VGF) techniques in conjunction withACRT have been found to be most suitable and successfully employed for growingternary crystals with a wide range of alloy compositions. In this chapter, we willdiscuss various concepts using GaInSb as a model material due to the extensivenature of work that has been carried out on this system. The growth processesdeveloped for GaInSb have been found to translate well to other alloy systems suchas GaInAs, InAsP and AlGaSb with appropriate modifications for vapor-pressurecontrol. The growth results from these crystals will not be presented here sincethey are still in the initial stages of development.