晶格匹配InAs/AlSb超晶格材料的分子束外延生长研究
Growth of lattice matched InAs/AlSb superlattices by molecular beam epitaxy
-
摘要: InAs/GaSb超晶格是量子级联激光器(quantum cascade lase, QCL)和带间级联激光器(interband cascade lasers, ICL)结构中重要的组成, 特别是作为 ICL的上下超晶格波导层是由大量的超薄外延层(纳米量级)交替生长而成, 细微的晶格失配便会直接导致材料晶体质量变差, 而且每层的厚度和组分变化会强烈影响材料结构性能. 论文研究验证了 InAs/GaSb超晶格材料生长的最佳温度约在420 ℃. 通过在衬底旋转的情况下生长40周期短周期GaSb/AlSb和InAs/GaSb超晶格, 并采用XRD测量拟合获得了GaSb和AlSb层厚分别为5.448 nm和3.921 nm, 以及InAs和GaSb层厚分别为8.998 nm和13.77 nm, 误差在10%以内, 获得了 InAs/AlSb超晶格的生长最优条件. 在GaSb衬底上生长晶格匹配的40周期的InAs/AlSb超晶格波导层, 充分考虑飘逸As注入对InAs/AlSb超晶格平均晶格常数的影响, 在固定SOAK时间为3 s的条件下, 通过变化As压为1.7×10–6 mbar来调整个超晶格的平均晶格常数, 实现了其与GaSb衬底晶格匹配. 实验结果表明超晶格零阶卫星峰和GaSb衬底峰重合, 具有完美的晶格匹配, 尖锐的次阶卫星峰和重复性良好的周期结构也表明优异的超晶格材料结构质量.Abstract: The InAs/GaSb superlattices (SPLs) is an important component of quantum cascade laser (QCL) and interband cascade laser (ICL). In particular, the upper and lower SPL waveguide layers of the ICL are alternately grown from a large number of ultra-film epitaxial layers (nm) by molecular beam epitaxy(MBE). Subtle lattice mismatch may directly lead to the deterioration of material crystal quality, and the change of thicknessand the composition of each layer will strongly affect the structural performance of device material. The optimal growth temperature of InAs/GaSb SPLs is about 420 ℃. By growing GaSb/AlSb and InAs/GaSb SPL both with 40 short periods under the substrate rotating, the thickness of GaSb layer and AlSb layer are 5.448 nm and 3.921 nm, and the thickness of InAs layer and GaSb layer are 8.998 nm and 13.77 nm, respectively. The error is within about 10%, and the optimal growth conditions of InAs/AlSb SPLs are obtained. A lattice matched 40-period InAs/AlSb superlattice waveguide layer is grown on GaSb substrate. The influence of drifting As injection on the average lattice constant of InAs/AlSb superlattice is fully considered. Under the condition of fixed SOAK time of 3 s, the As pressure is changed to 1.7 × 10–6 mbar to adjust the average lattice constants of the superlattices and achieve their matching with the GaSb substrate lattice. The experimental results show that the 0 order satellite peak of the SPL coincides with the peak of the GaSb substrate, and has a perfect lattice matching, and that the sharp second order satellite peak and the periodic structure good repeatability also indicate that the superlattice material has the excellent structural quality of the SPLs structure.