强化换热对CdZnTe晶体生长过程的影响

为了优化CdZnTe晶体生长过程的工艺参数,利用数值模拟方法研究了强化换热对晶体生长过程固液界面凹陷、溶质组分偏析的影响.结果表明:当坩埚轴向散热强度大幅度增加时,固液界面前沿的对流显著增强;随着凝固过程的进行,固液界面凹陷深度先是显著减小,随后显著增加;晶体起始段溶质组分的径向偏析明显减小,溶质组分轴向等浓度区增长.当坩埚侧面径向散热强度增加时,固液界面前沿的对流和界面凹陷深度先是有所减弱,随后又有较大增加.当坩埚内壁碳膜厚度增加时,界面前沿的对流强度显著减弱,而固液界面凹陷深度明显增加.径向散热和碳膜厚度的增加皆不能明显影响晶体内溶质组分分布.

Influence of enhancement of heat exchange on CdZnTe crystal growth process

In order to optimize the control parameters of CdZnTe single crystal growth with vertical Bridgman method, the influences were investigated of the enhancement of heat exchange, such as increasing the axial outward heat flux of the crucible bottom, the radial outward heat flux of the crucible wall, the carbon film thickness on the crucible inner wall, et al, on CdZnTe crystal growth process. When the axial outward heat flux of the crucible bottom is magnified ten times, the melt convection near the solid-liquid interface gets enhanced in a great deal, the interface concavity reduces extraordinarily at the beginning of the solidification process, but increases a lot later. The radial solute segregation decreases evidently in the initial part of the crystal (about one fourth of the whole ingot) , and the length of the axial iso-concentration zone increases a little. When the axial outward heat flux of the crucible bottom is magnified fifty times, negative radial segregation and positive axial segregation come into being in the initial part of the crystal. When the radial outward heat flux of the crucible wall is magnified, both the melt convection and the interface concavity reduce at the beginning of the solidification process, but increases a lot later. The increase of the carbon film thickness results in a notable reduction of the melt convection, and a great increase of the interface concavity. Nevertheless , both of them, the increases of the radial outward heat flux and the carbon film thickness, could hardly affect the solute segregation of the crystal.