Toward Monolithic Power Integration: β-Ga2O3 Devices and Circuits
This dissertation develops beta-phase gallium oxide devices and circuits for monolithic power integration.
Overview
Data centers, electric vehicles, heavy-duty robots, and drones all rely on power converters that efficiently handle high power. Gallium nitride (GaN) is the leading choice below 1 kV, while silicon carbide (SiC) leads above that range. Beta-phase gallium oxide ($β-Ga_{2}O_{3}$) is a promising material for next-generation power electronics. It has an ultrawide bandgap of 4.8 eV, a critical field of about 8 MV/cm, and a higher Baliga figure of merit than GaN or SiC. It is also the only ultrawide-bandgap material that can be grown from the melt, enabling low-cost, large-diameter wafers.
Vertical Schottky diodes with AlN passivation reach breakdown voltages of 1.2–1.3 kV, a specific on-resistance of about 10 mΩ·cm2, and a rectification ratio of 1010 at temperatures up to 400 °C. A recessed-channel, enhancement-mode lateral MOSFET achieves an intrinsic gain of about 104 and a +5 V threshold voltage. It combines the high gain and low saturation voltage of source-gated transistors with higher on-current.
The devices are then combined into circuits. A compact resistor–transistor logic (RTL) inverter, which integrates MOSFETs with recessed-epitaxy resistors, occupies 0.785 mm2. It provides a 0–15 V output swing, switches at 106.4 kHz, and operates reliably at temperatures up to 125 °C. Using this inverter as a level shifter, together with an enhancement-mode push–pull buffer with a bilayer gate dielectric, enabled a monolithic gate-driver IC. The driver switches an 840 pF power-MOSFET gate load at 716 kHz, with a 0–7.5 V output and an 8.4 mA drive current. This is an important step toward $β-Ga_{2}O_{3}$ power ICs.
Finally, optimizing the recess depth increased the MOSFET current density to 15–25 mA/mm. At power densities above 120 W/cm2, a current kink appears and can cause self-heating-induced gate-dielectric failure. The dissertation evaluates AlN passivation as a passive cooling approach and concludes with directions for building a power IC entirely on a shared $β-Ga_{2}O_{3}$ platform.
Presenters
Brief Biography
Ganesh Mainali is a Ph.D. candidate in Electrical and Computer Engineering at KAUST, where he conducts research in the Advanced Semiconductor Laboratory under the supervision of Prof. Xiaohang Li. Before joining KAUST, he earned an M.S. in Electronic Engineering from Kwangwoon University, South Korea, in 2021.
