垂直Bridgman法生长Cd_(1-x)Mn_xTe晶体的缺陷研究

Study on Defects in Cd_(1-x)Mn_xTe Crystals Grown by Vertical Bridgman Method

本文采用垂直布里奇曼（Bridgman）法生长了尺寸为30 mm×130 mm的Cd1-xMnxTe晶体,利用Nakagawa腐蚀液显示了晶体的位错、Te夹杂相和孪晶缺陷,并采用傅立叶变换红外光谱仪研究了晶体的红外透过率与晶体缺陷之间的关系。结果表明：生长态Cd1-xMnxTe晶体的位错密度为104~105cm-2,Te夹杂相密度为103~104cm-2,晶体中的孪晶主要为共格孪晶,孪晶面为{111}面,且平行于晶体生长方向。在入射光波数4000~500 cm-1范围,晶体的红外透过率为36.7%~55.3%,红外透过率越大,表明晶体的位错和Te夹杂相密度越低,晶体对该波长范围的红外光表现为晶格吸收和自由载流子吸收。

Cd1-xMnxTe single crystal with the dimensions of 30 mm×130 mm were grown by vertical Bridgman method.The structural defects of dislocations,Te inclusions and twins in the as-grown crystal were effectively revealed by the Nakagawa etchant,and the relation between IR transmitance and defect was investigated by the Fourier-transform infrared（FT-IR） spectra.The results indicated that the etch pits density in the crystal was of 104-105 cm-2 and the Te inclusion density of 103-104 cm-2.The twins observed in the as-grown ingot were mainly coherent ones,which lay on the {111} face and ran parallel to the growth axis of the ingot.The IR transmittance of the as-grown wafers under the incident IR wavenumber range of 4000-500 cm-1 was in the range of 36.7%-55.3%.Crystals with higher IR transmittance reflect lower dislocation density and lower Te inclusion density.It is found that the lattice absorption and free carrier absorption to the IR from 4000-500 cm-1 are the main absorption mechanics involved in the FT-IR spectra in Cd1-xMnxTe crystals.