New Surface Chemistry and Adatom Kinetics Results in Novel Extreme Bandgap Semiconductor Device Opportunities

Novel, low thermal budget synthesis methods have resulted in breakthroughs in AlN and AlScN epitaxy. New surface kinetics and chemistry discoveries including enhanced adatom diffusion at low temperatures, enhanced defect and impurity control. Catalytic induced decomposition of plasma excited molecular nitrogen has resulted in ~3x increases in growth rates and is shown to be key to metal rich single-phase AlScN epitaxy at low temperatures (~400°C). Absent this effect, AlN can still be grown metal rich at ~600°C, 400-800°C less than other synthesis methods. These physics discoveries have paved the way for a variety of new devices and applications. An 80-year-old roadblock has been shattered wherein Aluminum Nitride (AlN) was successfully doped, achieving both substantial p and n-type conductivity. In breaking this barrier, commercial epitaxy tools were used in a new unexpected way, to convert AlN from merely an insulator to a viable semiconductor, the largest direct bandgap semiconductor (6.1 eV) ever discovered. Augmenting the many deep UV optoelectronic opportunities, because of AlN's large bandgap energy, AlN has – by far – the highest Johnson and Baliga figures of merit (figures of merit describing transistor viability) of any semiconductor that has a commercial substrate making it the most promising commercially viable semiconductor for high temperature, high voltage and high-power electronics. When Scandium is added to AlN, a remarkable emerging piezo/ferroelectric semiconductor is formed with acoustic applications predicted to extend to 50 GHz operation. Additionally, AlScN has been shown by Ga Tech to result in record transistor channel conductivity of 150 ohms/square implying that AlScN can augment AlN's remarkable high temperature and high voltage capability with ~2.5 times higher current capability compared to AlGaN/GaN state-of-the-art High Electron Mobility Transistors (HEMTs).