In situ studies of Cd1-xZnxTe nucleation and crystal growth

The nucleation and growth of Cd1-xZnxTe crystals in a multi-zone vertical B ridgman growth furnace have been observed and measured using in situ eddy c urrent sensor techniques. A two-coil eddy current sensor measured coil impe dance changes for multifrequency which were then interpreted using an elect romagnetic finite element analysis. The sensor was used to characterize the initial melting of a charge and the subsequent nucleation of solid during solidification. Fully remelted in situ compounded charges were exposed to s ignificant melt superheating and were found to undergo large melt undercool ings (of up to 20 degrees C), spontaneous crystal nucleation and rapid soli dification (velocities approaching 60 mm/h which was more than 10 times the furnace translation rate). Post-growth metallography revealed that about 2 0 mm of polycrystalline solid was formed in this way before recalescence ar rested the solidification interface. In partially remelted charges neither undercooling nor unstable growth were observed. These results indicate that eddy current sensors can be used to monitor critical aspects of the vertic al Bridgman crystal growth of semiconducting materials and may simplify the implementation of seeded crystal growth concepts in this, and other, semic onductor crystal growth processes. (C) 2000 Elsevier Science B.V. All right s reserved.