Design and Optimization of $\boldsymbol{\beta}$-Ga2O3 on (h-BN layered) Sapphire for High Efficiency Power Transistors: A Device-Circuit-Package Perspective

Despite exceeding the Baliga's Figure of Merit (BFOM) by 400% and Huang's Chip Area Manufacturing FOM (HCAFOM) by 330% [1], the performance of existing $\beta$-Ga2O3 FETs is inferior to that of GaN, primarily due to extreme self-heating. Self-heating effect (SHE) has emerged as an important concern for device performance, output power density, run-time variability and reliability for modern logic transistors. The effects are even more severe for high-power transistor where the channel material may be a poor thermal conductor, e.g. $\beta$-Ga2O3. Very high internal electric fields, extreme temperature and mechanical stresses associated with these transistors drive electrochemical reactions [2], influence atomic processes [3], and accelerate multiple non-equilibrium effects [4]. A device-circuit-package, multi-physics, multi-scale simulation is needed to capture these effects self-consistently, but such a model has not yet been developed. In this paper, we (i) develop the first self-consistent device (TCAD), circuit (HSPICE), and package (COMSOL) model considering SHE which predicts FET performance on variety of substrates accurately; (ii) use the model to propose a novel hexagonal-Boron Nitride (h-BN) based $\beta$-Ga2O3 FET with 30% (cf. Sapphire substrate) and 80% (cf. SiO2 substrate) reduction in thermal resistance $(R_{th})$; (iii) demonstrate the performance of boost converter (with parameters extracted from our TCAD model) with h-BN based $\beta$-Ga2O3 FET, which outperforms the existing $\beta$-Ga2O3 FETs, achieving an efficiency within 10-15% of highest performing enhancement mode (E-mode) GaN FET; (iv) propose h-BN based FinFET which exceeds the ION of the existing $\beta$-Ga2O3 FET by more than 500%; and (v) develop a Faraday-cage type novel packaging strategy for effective heat dissipation and efficient system performance in $\beta$-Ga2O3 FETs.