Zn_(1-x)Mn_(x)/ZnSe应变超晶格分子束外延生长及光学特性研究

Molecular Beam Epitaxy and Optical Properties ofZn_(1-x)Mn_(x)/ZnSeStrained Layer Superlattices

用分子束外延方法在ＧａＡｓ（１００）衬底上成功生长了高质量的Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ（ｘ＝０．１６）超晶格结构，用Ｘ射线衍射和低温光致发光（ＰＬ）对其结构、应变分布以及光学性能进行了研究。结果表明，２Ｋ温度下，Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ超晶格的光致发光中主发光峰对应于ＺｎＳｅ阱中基态电子和基态轻空穴之间的自由激子跃迁，而且其峰位相对于ＺｎＳｅ薄膜材料的自由激子峰有明显移动。其中，当超晶格的总厚度大于其临界厚度时，自由激子峰位向低能方向红移２ｍｅＶ；当超晶格总厚度小于其临界厚度时，自由激子峰位向高能方向蓝移６ｍｅＶ。理论上分析计算了由应变和量子限制效应引起的自由激子的峰位移动，理论和实验符合很好。

? Zn 1-x Mn x Se / ZnSe  strained layer sperlattices are grown by molecular beam epitaxy on GaAs(100) substrates and characterized by X ray diffraction and low temperature photoluminescence. The main emission peaks in photoluminescence spectra can be attributed to the free exciton between the lowest electron subband and ground light hole subband of the ZnSe well. For the case where the total thickness of a  Zn 1-x Mn x Se / ZnSe  superlattice is well bellow the critical value, the structure grows pseudomorphically to the buffer layer. The ZnSe well layer is free of strain and the  Zn 1-x Mn x Se  layer is under compressive strain. A blue shift of 6 meV of the excitonic peak is observed and has been explained by the carrier confinement effect only. For the case of a  Zn 1-x Mn x Se / ZnSe  superlattice with a thickness larger than its critical values, we show that it can be treated as free standing with ZnSe under tension and  Zn 1-x Mn x Se  under compression. The strain present can overwhelm the quantum cofinement to produce a net red shift of 2 meV of the near band edge feature. The energy shifts due to the strain and quantum confinement are calculated on the basis of deformation potential theory and Bastard′s method, showing good agreement with the experimental results.