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Title: Understanding and Controlling Surface Kinetics of III-Nitride Epitaxy Toward Next-Generation Semiconductor Devices
Committee:
Dr. Doolittle, Advisor
Dr. Hunt, Chair
Dr. Losego
Abstract: The objective of the proposed research is to understand and apply the fundamental growth kinetics for III-nitride semiconductors. III-nitrides have the potential to be used for a wide array of impactful semiconductor device applications, including full-spectrum/tandem-with-silicon solar cells, RGB LEDs, UV LEDs and lasers, and high-power diodes and transistors. However, many of these applications remain unrealized or too inefficient to be useful due to challenges in growing high-quality ternary III-nitride material by traditional growth techniques like metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). Through control of growth kinetics, metal-modulated epitaxy (MME) has been shown to have success in growing III-nitrides, especially ternary alloys with compositions in the miscibility gaps unreachable by other techniques. When combined with other achievements of MME, particularly good p-type doping of III-nitrides, this control of growth kinetics is expected to lead to the realization of devices that have driven interest in this material system but have thus far been unachievable. The first step in achieving devices that rely on high quality, ternary III-nitride semiconductor films (AxB1-xN) is understanding why these ternaries separate into A-rich and B-rich regions. A kinetic model has been developed to formalize a description of the known and hypothesized mechanisms that are operative during the epitaxial growth of these films. The model consists of a system of coupled differential equations describing these mechanisms as stochastic rates that act on the A- and B-cations in the semiconductor crystal and the surface adlayers. The proposed research will be dedicated to defining the model’s free parameters and using it to plan the growth of devices from the literature that have either only been evaluated theoretically or that need significant improvement to be competitive with other materials.
