Lattice-matched nitride-oxide HEMTs with superior electronic and thermal performance

Abstract

β-Ga2O3 has gained significant interest for applications in high-power devices because of its large energy bandgap of Eg = 4.4–4.8 eV, a high breakdown field of ∼7–8 MV/cm, and availability of melt-grown large area bulk substrates. (AlxGa1−x)2O3/Ga2O3-based heterostructure devices have also been realized for high-power and high-frequency applications. The performance of these devices is, however, limited by the low conduction band offsets resulting from difficulties in growing high-Al composition β-(AlxGa1−x)2O3. Additionally, low thermal conductivity of β-Ga2O3 can result in severe self-heating effects and potential early failure of devices, restricting its application in high temperature and high-power electronics. In this work, an in-depth analysis of lattice mismatch in the heterojunctions between (0001) oriented III-nitrides (AlN, GaN, BN, and InN) and (2¯01) oriented β-phase III-sesquioxides (Al2O3, Ga2O3, and In2O3) and their alloys is conducted. An AlN/β-(In0.21Ga0.79)2O3 heterojunction is found to have good lattice match with high conduction band offset along with a polarization charge induced 2-dimensional electron gas (2DEG) at the interface with density ∼23× the theoretically maximum 2DEG carrier density achievable in β-(Al0.2Ga0.8)2O3/Ga2O3 interface. Through detailed thermal simulations under different cooling conditions, we show significantly lower self-heating effect (RTH reduction of ∼41%) in AlN/β-(In0.21Ga0.79)2O3 high electron mobility transistors (HEMTs) compared to β-(Al0.2Ga0.8)2O3/Ga2O3-based HEMTs. Additionally, a physics-based compact model is used to calculate practically achievable current density in the presence of self-heating effects in these structures. For similar temperature rise, AlN/β-(In0.21Ga0.79)2O3 HEMTs are found to be ∼5× superior in terms of current carrying and power handling capability compared to β-(Al0.2Ga0.8)2O3/Ga2O3 HEMTs.