Classical semiconductor
Distribution and genesis of inclusions in CdTe and (Cd,Zn)Te single crystals grown by the Bridgman method and by the travelling heater method

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Abstract

The density and distribution of inclusions of the excess component in CdTe and (Cd,Zn)Te crystals grown by the Bridgman method and by the travelling heater method (THM) have been investigated by transmission infrared (IR) microscopy. A correlation between composition of the metl (melt-solution) and inclusion density has been found. An inclusion-free CdTe Bridgman crystal was grown using a Cd overpressure, a source temperature of 850°C and a melt temperature of 1118°C. The highest inclusion density was detected in a (Cd,Zn)Te THM crystal grown from a Te-rich zone under microgravity conditions. For the first time the kinetics of the inclusion genesis are discussed in detail. The inclusion morphology is very sensitive to the temperature field. In contrast to as-grown crystals, cooling down solution-grown crystals in a very small temperature gradient causes a symmetrical inwards crystallization of the solution as entrapped droplets. In a large temperature gradient, temperature gradient zone melting (TGZM) of the included droplets occurs. Their migration results in {111} facet development at the dissolving interface, although the growing interface is rounded.

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Present address: Institut für Kristallzüchtung, Rudower Chaussee 6, D-12489 Berlin, Germany.

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