Improvement of Breakdown Voltage and ON-Resistance in Normally-OFF AlGaN/GaN HEMTs Using Etching-Free p-GaN Stripe Array Gate
Xing Wei, Xiaodong Zhang, Chi Sun, Wenxin Tang, Chunhong Zeng, Fu Chen, Tao He, Guohao Yu, Liang Song, Wenkui Lin, Xuan Zhang, Desheng Zhao, Wei Huang, Yong Cai, Baoshun Zhang
Abstract
In this article, the normally- OFF etching-free p-GaN stripe array gate AlGaN/GaN high-electron-mobility-transistors (PSAG-HEMTs) are designed and experimentally demonstrated through hydrogen plasma treatment. The unique threshold voltage (<inline-formula> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula>) modulation technique based on the PSAG structure is proposed and simulated. Using this method, the <inline-formula> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> can be continuously shifted from −0.14 to +1.03 V by just tuning the widths of p-GaN (<inline-formula> <tex-math notation="LaTeX">${W}_{p}$ </tex-math></inline-formula>) and hydrogenated p-GaN (HR-GaN) stripes. To improve breakdown voltage (BV), the PSAG is extended to the drain side based on the 3-D simulation results so that a new electric-field peak is introduced at the edge of the PSAG in the drain side and then the surface electric field is optimized. Besides this, an enhanced conductivity effect is observed and results in a low ON-resistance. The fabricated PSAG-HEMT with <inline-formula> <tex-math notation="LaTeX">$0.75~\mu \text{m}~{W}_{p}$ </tex-math></inline-formula> and 4-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> extension length (<inline-formula> <tex-math notation="LaTeX">${L}_{E}$ </tex-math></inline-formula>) exhibits a positive <inline-formula> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> of +0.8 V, a low specific ON-resistance (<inline-formula> <tex-math notation="LaTeX">${R}_{\text {ON,sp}}$ </tex-math></inline-formula>) of 2.73 <inline-formula> <tex-math notation="LaTeX">$\text{m}\Omega \cdot cm^{2}$ </tex-math></inline-formula>, a high BV of 852 V (1449 V) at <inline-formula> <tex-math notation="LaTeX">${I}_{D} = 1 ~\mu \text{A}$ </tex-math></inline-formula>/mm, and BFOM of 266 MW/cm<sup>2</sup> (769 MW/cm<sup>2</sup>) with substrate grounded (floating), which demonstrate significant improvements over Reference single-gate E-mode and D-mode devices. This work provides a promising architecture for future high voltage normally- OFF p-GaN HEMT devices.