Numerical analysis of Cd_1-xZn_x Te crystal growth by the vertical Bridgman method using the accelerated crucible rotation technique

The growth process of CdZnTe crystals by the vertical Bridgman method (VBM) using the accelerated crucible rotation technique (ACRT) has been numerically analyzed by the finite-difference method. The forced convection resulting from ACRT and its effects on the position and the shape of the melt/crystal interface are studied, and the solute redistribution and radial segregation are evaluated. The results show that during the ACRT process the convection vortex in the melt appears, develops, declines and disappears periodically according to the periodic change of the crucible rotations. Corresponding to the periodic change of the flow field, the growth rate, the temperature and concentration oscillate periodically. When ACRT with a certain crucible rotation type is applied to the Bridgman crystal growth process of CdZnTe, the interface depth increases markedly. "The discontinuous triangle wave" type which has the rotational reversal and includes the accelerated, decelerated and rest period is a proper one. For a CdZnTe crystal with a radius of 0.75cm, the period (T_ACRT) of 24s and the maximum rotation rate (ω_max) between 30 and 50rpm are preferable.