Zn_(1-x)Mn_xSe/Zne应变超晶格的分子束外延生长及特性研究

Molecular Beam Epitaxy and Characterization of Zn_(1-x)Mn_xSe/ZnSe Superlattices on (100) GaAs Substrates

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，x＝0．14）超晶格结构．用X射线衍射和喇曼散射对其结构、应变分布以及光散射性能进行了研究．当超晶格的总厚度大于其临界厚度时，超晶格将完全弛豫至一个新的平衡晶格常数．此时，在（100）平面内，ZnSe阱层受到张应变，而Zn1-xMnxSe垒层受到压应变，从而，导致其喇曼光谱中，ZnSe阱和Zn1-xMnxSe垒的LO声子峰分别向低频方向和高频方向移动．当超晶格总厚度小于其临界厚度时，超晶格不再弛豫而是保持过渡层Znse的晶格常数，此时，ZnSe阶层不再受到应变，而Zn1－xMnxSe垒层受到压应变，在其喇曼光谱中，仅视察到ZnSe材料光学声子峰．本文从理论上分析计算了由这种应变引起的LO峰的频率移动，结果和实验所测值符合很好．

High quality Zn1-xMnxSe/ZnSe strained-layer superlattices are grown by molecular beam epitaxy on GaAs (100) substrates and characterized by X-ray diffraction and Raman scattering. For the case of a Zn1-xMn.Se/ZnSe superlattice with a larger thickness than a critical thickness, we show that it can be treated as free-standing with ZnSe under biaxial tension and Zn1-xMnxSe under biaxial compression, while the frequency shifts of LO phonons are observed both in ZnSe well layer and Zn1-xMnxSe barrier layer. For the case where the total thickness of a Zn1-xMn.Se/ZnSe superlattice is well bellow the critical thickness, the structure grows pseudomorphically to the buffer layer. In this case, the ZnSe well layers are not strained and Zn1-xMnxSe is under biaxial compressive strain. No shift of Raman frequency is observed in Raman spectrum. the frequency shifts of LO phonons due to the lattice mismatch between the continuent layers are calculated, showing a good agreement with that of theoretical calculations.