| The purpose of this research has been to investigate the optical properties of III-V nitride-based materials. Applications of III-V nitride materials include blue, green light emitting diodes and laser diodes, high power and high frequency electronic devices. The initial stage of this thesis involved photopumped stimulated emission observations, and gain coefficient measurements. Threshold pump power densities for stimulated emission and gain coefficients for InGaN/GaN single heterostructures were measured. This research also involved observations of tunable emission from InGaN multiple quantum wells. Considerations were given to donor-acceptor recombination, changes in the binding energy of impurity due to the quantum confinement, band-filling effects, piezoelectric field induced changes in the emission energy as processes likely to be responsible for the tunable emission from the InGaN/GaN quantum wells. This thesis also contains studies of persistent optical effects such as optical metastability in bulk GaN single crystals and reconfigurable optical properties in InGaN/GaN heterostructures. For the case of bulk GaN single crystals, it was observed that a new emission band emerged on the emission spectra after the sample was exposed to ultra-violet laser light. Reconfigurable optical properties in InGaN/GaN heterostructures were used to create high-contrast optical patterns on the sample at room and liquid nitrogen temperatures. Based on this effect, optical data storage was realized in InGaN/GaN heterostructures. This work help design light-emitting devices and novel optical information storage systems. |
