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Title: Investigation of Metal Modulated Epitaxy Grown III-Nitride High-power Electronic and Optoelectronic Devices
Committee:
Dr. Alan Doolittle, ECE, Chair, Advisor
Dr. Douglas Yoder, ECE
Dr. John Cressler, ECE
Dr. Asif Khan, ECE
Dr. Eric Vogel, MSE
Abstract: The wide-bandgap material GaN (Eg = 3.4 eV) continues to mature due to its achievements in high-power electronic and optoelectronic devices. The fully vertical GaN high-power devices show high performance but are very expensive. Quasi-vertical GaN devices are cost-effective but lack high performance due to low quality films. Improvement in the performance of quasi-vertical devices would make this technology suitable for high volume production. Although the market of GaN based devices is still growing, significantly higher performance parameters can potentially be achieved with the ultrawide-bandgap semiconductor material AlN with the bandgap as high as 6.1 eV. The only limitation to AlN-based devices so far was doping. An extensive study is performed to explore the 3D phase diagram of MME to find the optimized morphological, electrical, structural, and optical growth conditions to achieve high performance high-power quasi-vertical GaN pin diodes. Thick abrupt Beryllium step-doped GaN i-layers were used to demonstrate these high-power devices. Novel fabrication methods and current spreading layers are introduced in these devices. Furthermore, for the first time in more than 8 decades of AlN research, substantial bulk conduction, both p-type and n-type, was achieved in MME AlN and the first known p-n junction AlN diodes are demonstrated to extend the high-power performance of nitride technology. Also, MME mixed AlN/GaN Pin and junction barrier Schottky diodes are demonstrated to achieve low turn-on voltage and higher breakdown performance simultaneously. The conductive AlN films show great promise for AlN-based device applications that could potentially revolutionize deep ultraviolet light based viral and bacterial sterilization, polymer curing, high-temperature, high-voltage and high-power electronics among many societal impacts.
