Effects of axial vibration on vertical zone-melting processing

Vibration can be an effective way for controlling heat flow and the growth interface during crystal growth. To better understand the role of axial vibration in vertical zone melting, an important process for crystal growth and purification, computer simulation is performed. For the zone melting of a 2-cm GaAs crystal in a quartz ampoule, simulation results show that an axial vibration, especially at high frequency, can significantly affect the flows and further the growth interface. The concave growth front due to buoyancy convection can be also inverted easily to a convex one. The effects of vibration frequency are further illustrated, and the validity of the high-frequency model is examined. For GaAs, the resonance frequency is found at about 0.5 Hz, where significant flow oscillation and severe periodic growth and remelting can be induced. (C) 2000 Elsevier Science Ltd. All rights reserved.