Growing Single Crystals with a Low Melt Height and an Axial Vibration

Single crystal growth of antimony-doped germanium is investigated by the vertical Bridgman (VB), axial heat processing (AHP), and axial vibrational control (AVC) methods. In the VB method, the existence of a radial temperature gradient in the melt leads to an inhomogeneous solute distribution which affects the quality of the grown crystal. However, in the AHP growth, the melt height above the interface and the radial temperature gradient in the melt can be reduced by immersing a baffle with a high thermal conductivity. Consequently, the radial solute segregation can be reduced. In order to provide even a better solute homogeneity, the immersed baffle can be vibrated axially which forms the AVC growth. Seven Sb-doped Ge crystals are grown with the three mentioned methods in order to investigate the effect of the melt height, the pulling velocity, and amplitude and frequency of the vibration on the homogeneity of the solute distribution, the achieved single crystal length, the morphological stability, and the quality of the grown crystals. It is observed that a reduced melt height and appropriately adjusted vibration in the melt can improve the crystal quality. The interface stability has been analyzed by several criteria.