| Nitride semiconductor based light emitters have great potential as high power, high efficiency light sources in visible and ultra-violet (UV) wavelength range. The physics process in nitride semiconductor light emitters was studied through novel devices, such as vertical cavity and nano-size light emitters.; A number of GaN light emitters have been studied in detail, including blue and near UV RCLED and VCSEL, optically pumped edge-emitting laser at 340 nm, and light emitters with nano-size structure.; A number of fabrication process and key components have been developed. For example, high-resolution e-beam lithography has been used to fabricate GaN nanostructure devices with size below 100 nm. The devices have been characterized in detail by various of techniques including optical pumping experiment and time-resolved PL measurement. Through the research on GaN devices, physics such as optical gain spectroscopy and e-h pair lifetime have been studied.; Robust violet/blue light luminescence was observed from the dense GaN nanopost arrays, fabricated by top-down approach. The optically active nano-structures provided an opportunity to study the light-matter interaction. Strongly polarized emission from linear arrays and stimulated emission on micrometer lateral scale were the examples of the observations in the henceforth largely unexplored sub-wavelength regime. The strong stimulated emission near 400 nm wavelength from the dense 2D GaN nano-post arrays was especially interesting since the device is "resonatorless". Optical pumping and time-resolved photoluminescence techniques were used to understand its origin. The physics effect such as photonic crystal (PC) and random scattering in the sub-wavelength regime was analyzed. The results suggested new physics in the near field regime where local, near field electromagnetic effects may play a dominant role. |
