Group III nitride materials, especially gallium nitride (GaN), have been regarded as a promising material system for both electronic and optoelectronic applications, owing to their unique and superior properties, such as wide and direct energy bandgap, high critical electric field, good thermal conductivity, high energy efficiency and long lifetime. High-quality GaN epilayers have been successfully grown on bulk GaN, sapphire, SiC, and Si substrates. Among them, large-scale and low-cost Si substrate has made GaN-on-Si technology a key enabler for high-performance and cost-effective GaN-based devices. GaN-based vertical devices feature a large breakdown voltage for limited device size, excellent thermal performance, and high integration flexibility. Accordingly, it is highly desi...[ Read more ]

Group III nitride materials, especially gallium nitride (GaN), have been regarded as a promising material system for both electronic and optoelectronic applications, owing to their unique and superior properties, such as wide and direct energy bandgap, high critical electric field, good thermal conductivity, high energy efficiency and long lifetime. High-quality GaN epilayers have been successfully grown on bulk GaN, sapphire, SiC, and Si substrates. Among them, large-scale and low-cost Si substrate has made GaN-on-Si technology a key enabler for high-performance and cost-effective GaN-based devices. GaN-based vertical devices feature a large breakdown voltage for limited device size, excellent thermal performance, and high integration flexibility. Accordingly, it is highly desired to develop vertical GaN-on-Si devices and systems, yet there is still much room for improvement.

This thesis mainly focuses on the development of vertical GaN-on-Si devices and systems based on a vertical process using the Au-free Cu/Sn metallic bonding scheme.

For vertical devices, both fully- and quasi-vertical GaN-on-Si p-i-n diodes were fabricated with record performance and comprehensive comparison. Moreover, vertical-injection LEDs (VLEDs) have been developed with enhanced electroluminescence characteristics compared to conventional planar LEDs. Furthermore, VLEDs on a rigid carrier substrate can be lifted-off and attached to flexible substrates without evident degradation. The demonstrations of vertical p-i-n didoes and LEDs indicate the potential of GaN-on-Si technology for high-power and solid-state lighting applications.

For vertically-integrated systems, a monochromatic active matrix LED micro-display system was first demonstrated, combining a blue micro-LED array and a custom-designed CMOS backplane. The micro-display was extended to full-color by applying red and green QDs dispersed photoresist (QD-PR) on the pixels following the Bayer matrix configuration (RGGB). Therefore, the feasibility is verified for the monochromatic and full-color micro-display systems using GaN-on-Si technology, paving a new pathway toward volume production of LED micro-display in the near future.