半磁半导体Cd1-xMnxTe光吸收边的压力效应

本文研究了室温下1—40kbar流体静压力范围内三元化合物半磁半导体Cd_1-xMn_xTe光吸收边的压力效应。实验结果给出:x<0.5的样品,吸收边随压力增加向高能方向以α=6—8×10^-3eV/kbar的速率漂移,并具有10^-5/kbar²量级的二级非线性系数;x≥0.5的样品,表观吸收边随压力增加向低能方向漂移,压力系数为α-5×10^-3eV/kbar。高压下所研究的样品均有一从闪锌矿结构到NaCl结构的相变发生。这一相变可以是不可逆的,相变压力与样品组分有关,大致在25—40kbar范围内。根据半导体能带畸变势效应和晶体场理论模型估计了压力系数的理论值,讨论了不同压力系数的物理原因。关键词：

PRESSURE DEPENDENCE OF THE ABSORPTION EDGE OF SEMIMAGNETIC SEMICONDUCTORS Cd1-xMnxTe

The effect of pressure on the optical absorption edge for mixed crystals Cd_1-xMn_xTe with different manganese concentrations in the range of lbar to 40 kbar and at room temperature is reported. The observed absorption edge shifts to higher energy with increasing pressure at a rate of a = 6-8 ×10^-3 eV/kbar and a second order coefficient with the order of magnitude 10^-5 eV/kbar² for the samples with x<0.5; to lower energy with increasing pressure at a rate of a=-5.0×10^-3 eV/kbar for the samples with x≥0.5. A phase transition from zinc blende to NaCl-type structure occurs for all the samples studied. The transition pressures depend on the Mn contents in the samples in the region of 25—40 kbar. The physical origins of different pressure coefficients are discussed in the light of the deformation potentials of energy band slates and the hybridization of the Mn²⁺ 3d levels with the p-like states in the valence band.