Photoluminescence studies of carrier dynamics in (indium(x),aluminum(x)) gallium(1-x) arsenic/gallium arsenide quantum well structures

Abstract

This thesis discusses carrier dynamics of III-V semiconductor quantum well structures probed by photoluminescence techniques in In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs and Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs quantum well systems. Photoluminescence is a useful nondestructive probe of direct-gap quantum structures because the exciton population responsible for the measured luminescence is sensitive to well width, alloy composition, strain (in lattice-mismatched structures), and interface roughness. Continuous wave (cw) and time-resolved photoluminescence, and photoluminescence excitation (PLE) measurements were used to gain insight into the physics of GaAs alloy quantum structures.

The strain study in Chapter 4 measured the strain in individual quantum wells (within In$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs multiquantum well samples) by analyzing excitonic luminescence as a function of incident laser energy. These results led to the equilibrium strain model which describes strain due to lattice-mismatch being shared between well and barrier layers in strain-relaxed multiquantum well structures. The small feature study of Chapter 5 investigates the presence of an absorption dip in the photoluminescence spectra of an In$\sb{0.10}$Ga$\sb{0.90}$As single quantum well and five quantum well sample. The dip is explained by fast relaxation of mobile excitons from the barrier material into the quantum well layer. Chapter 6 investigates the effect of interface roughness on tunneling times between narrow well and wide well in Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs asymmetric coupled quantum well structures.