Title:  III-Nitride Homojunction Tunnel Junctions and Nitrogen Plasma Considerations for High Growth Rate Plasma-Assisted Molecular Beam Epitaxy

Committee: 

Dr. Doolittle, Advisor    

Dr. Frazier, Chair

Dr. Yoder

Abstract:

The objective of the proposed research is to improve the growth and fabrication of group-III nitride materials and devices via plasma-assisted molecular beam epitaxy. The III-nitride material system is explored due to its tunable direct bandgap from 0.7-6.2 eV, spanning from the infrared to deep ultraviolet wavelengths. Current state-of-the-art optoelectronic III-nitride devices are mainly composed of GaN and are thus most efficient in the blue visible wavelength regime. Materials relevant for the longer and shorter wavelengths remain immature due to a variety of growth related issues such as phase separation, decomposition, and insufficient p-type doping. Shorter wavelength devices in the ultraviolet range show promise in applications such as water and air purification and sterilization. Longer wavelength devices in the visible and infrared range are promising for high temperature concentrator solar cells and more efficient red and green light emitting diodes. Heavily doped GaN tunnel junctions are discussed and AlGaN tunnel junctions are proposed to improve current and next generation shorter wavelength device performances via improved contact resistances, current spreading, and the ability to series connect devices. Additionally, plasma considerations to form longer wavelength devices from high indium bearing III-nitrides via plasma-assisted molecular beam epitaxy technique are studied and optimized.