HgCdTe外延薄膜临界厚度的理论分析

基于在任意坐标系内应力与应变的关系、晶体弹性理论和位错滑移理论，研究了生长方向分别为［111］和［211］晶向，HgCdTe外延薄膜临界厚度与CdZnTe衬底中Zn组分和HgCdTe外延层中Cd组分的关系. 结果表明，HgCdTe外延薄膜临界厚度依赖于CdZnTe衬底中Zn组分和HgCdTe外延层中Cd组分的变化. 对于厚度为10μm，生长方向为［111］晶向的液相外延HgCdTe薄膜，要确保HgCdTe/CdZnTe无界面失配位错的前提条件，是CdZnTe衬底中Zn组分和HgCdTe外延层中Cd组分的波动必须分别在±0.225‰和±5‰范围内；而对于相同厚度，生长方向为［211］晶向的分子束外延HgCdTe薄膜，CdZnTe衬底中Zn组分和HgCdTe外延层中Cd组分的波动范围分别为±0.2‰和±4‰. 关键词： HgCdTe/CdZnTe 临界厚度 位错滑移理论 失配位错

Theoretical research on critical thickness of HgCdTe epitaxial layers

Based on the relationships between stress and strain in an arbitrary coordinate system, the elastic theory of crystal and the dislocation gliding theory, the critical thicknesses of HgCdTe/CdZnTe oriented in the ［111］ and ［211］ directions are calculated, and the dependence of the critical thickness of HgCdTe on substrate composition and film composition are studied. The results show that the critical thickness of HgCdTe depends sensitively on substrate composition and film composition. For 10μm films oriented in the ［111］ direction prepared by liquid phase epitaxy, the substrate composition and the films composition must match to within ±0.225‰ and ±5‰, respectively, to prevent the occurence of misfit dislocations. In addition, for 10μm films oriented in the ［211］ direction prepared by molecular beam epitaxy, the actual ranges of zinc composition and the films composition are ±0.2‰ and ±4‰ for the films to remain below the critical thickness, respectively.