Improvement of Breakdown Voltage and ON-Resistance in Normally-OFF AlGaN/GaN HEMTs Using Etching-Free p-GaN Stripe Array Gate

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 (
${V}_{TH}$
) modulation technique based on the PSAG structure is proposed and simulated. Using this method, the
${V}_{TH}$
can be continuously shifted from −0.14 to +1.03 V by just tuning the widths of p-GaN (
${W}_{p}$
) 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
$0.75~\mu \text{m}~{W}_{p}$
and 4-
$\mu \text{m}$
extension length (
${L}_{E}$
) exhibits a positive
${V}_{TH}$
of +0.8 V, a low specific ON-resistance (
${R}_{\text {ON,sp}}$
) of 2.73
$\text{m}\Omega \cdot cm^{2}$
, a high BV of 852 V (1449 V) at
${I}_{D} = 1 ~\mu \text{A}$
/mm, and BFOM of 266 MW/cm
²
(769 MW/cm
²
) 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.