Analytical Model and Structure of the Multilayer Enhancement-Mode β-Ga<sub>2</sub>O<sub>3</sub> Planar MOSFETs
Liangliang Guo, Suzhen Luan, Hongpeng Zhang, Lei Yuan, Yuming Zhang, Renxu Jia
Abstract
In this article, the planar <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> junctionless transistors with/without unintentional doping (UID) buffer layer are numerically investigated. It was found that the double-layer Ga<sub>2</sub>O<sub>3</sub> MOSFETs (epilayer/buffer layer) show a trade-off between threshold voltage (<inline-formula> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula>) and device reliability (resulting from anomalous Fe out-diffusion), as a function of the thickness (<inline-formula> <tex-math notation="LaTeX">${T}_{\text {buf}}$ </tex-math></inline-formula>) and carrier concentrations (<inline-formula> <tex-math notation="LaTeX">${N}_{\text {buf}}$ </tex-math></inline-formula>) of <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> buffer layer. The simulation results show that an adequate buffer layer (200 nm <inline-formula> <tex-math notation="LaTeX">$ < {T}_{\text {buf}} < {500}$ </tex-math></inline-formula> nm, <inline-formula> <tex-math notation="LaTeX">${N}_{\text {buf}} < {5}\times {10}^{{14}}$ </tex-math></inline-formula> cm<sup>−3</sup>) is beneficial to the pinch-off characteristic of <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> planar MOSFETs. A novel triple-layer MOSFET (introducing a low-doped <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> surface layer above the epilayer) is subsequently proposed and demonstrated to be an easy pathway to modulate <inline-formula> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula> by adjusting the thickness and doping concentration of surface layer. In addition, the effect of the lateral extension N<sup>+</sup> region is also discussed. As a result, the triple-layer <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> MOSFET with an optimized dimension can achieve positive enhancement-mode and better device performance: breakdown voltage (<inline-formula> <tex-math notation="LaTeX">${V}_{\text {br}}$ </tex-math></inline-formula>) and power figures of merit (P-FOM) are improved by 173.71% and 65.37%, respectively, while specific ON-resistance is increased by 391.35%.