Chapter 4 Structurally Induced States from Strain and Confinement

Publisher Summary This chapter presents a study on structurally induced states from strain and confinement. It discusses the many facets of strained-layer heteroepitaxy relevant to pseudomorphic growth, characterization, and device applications of such structures. The chapter presents a review of the models for strain relaxation in semiconductor overlayers on critical layer thicknesses. It describes the pioneering work on the structural properties of strained semiconductor multilayers. Coherently strained-multilayer structures consist of thin alternating layers of materials, which are lattice mismatched in bulk form but elastically strain to uniformly match up the lattice constants of the materials in the planes parallel to the heterointerface. The resulting value of the in-plane lattice constant ( a ‖ ) is intermediate between the unstrained lattice constants of the multilayer constituents. Progress in the fabrication of pseudomorphic semiconductor structures has led to numerous applications, including strained-layer photodetectors, enhanced-mobility field effect transistors, heterojunction bipolar transistors, light-emitting diodes, and photopumped as well as injection lasers that utilize strained layers.