ABSTRACT
A proper design of the active layers and injector layers is a vital step in producing sophisticated IIIN semiconductor laser structures. In order to generate the proper transition energies and probabilities to obtain optimal laser characteristics, one must carefully engineer the layer thicknesses andior layer compositions. Atomically resolved real-space scanning probe techniques are indispensable tools in optimizing and verifying the growth process. This chapter focuses on an InGaAs/InAIAs quantum cascade and a digital alloy quantum well laser structure with cross-sectional scanning tunneling microscopy. It shows the effect of rapid thermal annealing on the digital alloy quantum well structure. In the quantum cascade laser structure digital alloy grading was used to soften the barriers of the active region. The chapter describes that due to alloy fluctuations, softening of the barriers occur even without the digital grading. The roughening of the interfaces can be attributed to barrier/well intermixing due to the interdiffusion of AI and Ga atoms during annealing.
