Analysis, design, and testing of semiconductor intersubband devices

One of the characteristics of semiconductor intersubband devices is the large optical transition strength which can be exploited for novel electronic/optical device applications. Some notable intersubband devices are Quantum Well Infrared Photodetectors (QWIPs), Quantum Cascade (QC) lasers, and electron energy filters. This thesis deals with the theoretical analysis, optimized design, and testing of semi-conductor intersubband devices. An efficient numerical model has been developed to determine the dipole matrix element/optical transition strength in intersubband devices. A quasibound state model is presented which determines the effect of space charge density on the intersubband conduction band potential energy profile. An iterative global optimization technique based on simulated annealing for intersubband device performance parameters has been developed. The fourth numerical model quantifies the effect of spatially varying carrier effective mass on intersubband charge distribution and the quasi-Fermi level. The theoretical models are integrated into the design and optimization of a dual-band equal-absorption-peak QWIP whose absorption peaks fall in the mid (3–5 μm) and long (8–12 μm ) wavelength ranges of the atmospheric window. The absorption spectrum of the bicolor QWIP structure is verified through an infrared spectroscopic measurement. The experimental results show good agreement with the theoretical predictions, thus validating the theoretical tools developed in this thesis.