Improvement of Electron Transport Property and on-Resistance in Normally-OFF Al₂O₃/AlGaN/GaN MOS-HEMTs Using Post-Etch Surface Treatment

Abstract

Post-etch surface treatment technique was developed for normally-off recess-gate Al2O3/AlGaN/GaN metal-oxidesemiconductor high-electron-mobility transistors (MOS-HEMTs). By removing the residues and smoothing surface morphology after plasma etch, the diffusion-controlled interface oxidation (DCIO) and wet etch in MOS-HEMTs leads to a decrease in interface traps from 1.04×10 12 cm-2 to 6.3×10 11 cm-2 with filling voltage of 12 V. Field-effect mobility extracted in the linear region is 48 cm 2 /V• s for MOS-HEMTs with an optimized post-etch surface treatment process, 33% larger than the case with conventional chemical clean process. Due to the increased electron mobility and decreased sheet resistance beneath the gate by over 30%, normally-off MOS-HEMTs with DCIO and wet etch exhibit a remarkable increase in output current by about 29% and an increase in peak transconductance from 35 mS/mm to 41 mS/mm. The optimized post-etch surface treatment method also enhances blocking voltage from 120 V to 230 V, by suppressing the leakage current resulting from gate soft breakdown. Dynamic characterization shows that the normalized on-resistance is increased by double with drain stress up to 80 V, and various post-etch surface treatment process has little effect on current collapse. Two types of threshold voltage shifts caused by interface trapping and border trapping are observed in the normally-off MOS-HEMTs, which keeps stable with an increase in temperature up to 125 ℃. Index Terms-AlGaN/GaN, interfacial engineering, metaloxide-semiconductor high-electron-mobility transistors (MOS-HEMTs), normally-off, post-etch surface treatment. I. INTRODUCTION WING to the superior properties such as high power density, high efficiency, low on-resistance, and compact size, GaN-based high-electron-mobility transistors (HEMTs) are promising candidates for high-speed power electronics.

Performance improvement of enhancement-mode GaN-based HEMT power devices by employing a vertical gate structure and composite interlayers*

“…Tables 2 and 3 summarize the device performances of the proposed VG-HEMT, JVG-HEMT, PVG-HEMT, and the reported E-mode HEMTs [25,26]. It can be seen that the PVG-HEMT has a higher V th of 3.6 V and a higher BV of 1129 V, while the JVG-HEMT has a higher I DS of 752 mA mm −1 and a lower R on of 0.56 mΩ•cm 2 .…”

“…It is noted that the device FOM value can be further boosted when an additional field plate (for example, 0.5 µm field plate at the gate corner toward the drain side) is employed. Figure 15 compares the performance of the reported E-mode HEMTs [25][26][27][28][29][30][31][32][33][34][35][36] and the proposed devices in this work. The overall performance of JVG-HEMTs and PVG-HEMTs are much closer to the theoretical material limit of GaN, suggesting the great potential of our proposed vertical gate structures featuring composite interlayers.…”

“…In the actual experiments, there will be several issues that need to be addressed, particularly regarding the formation of ohmic contacts in the recessed region, selective epitaxial growth, interface quality and etching retreatment. Performance comparison among the reported E-mode HEMTs [25][26][27][28][29][30][31][32][33][34][35][36] and the proposed VG-HEMT, JVG-HEMT, and PVG-HEMT devices (Exp. Works: [25][26][27][28][29][30][31][32][33][34][35].…”

“…Performance comparison among the reported E-mode HEMTs [25][26][27][28][29][30][31][32][33][34][35][36] and the proposed VG-HEMT, JVG-HEMT, and PVG-HEMT devices (Exp. Works: [25][26][27][28][29][30][31][32][33][34][35]. ; Sim.…”

Advancements in energy efficientGaNpower devices and power modules for electric vehicle applications: a review

“…156 The post-etch surface treatment is so useful for improvising the R on and electron transport property. 157 It is also important to estimate the dR on more accurately. An excellent frame work is proposed for the inclusion of dR on estimation in various manufactures data sheets.…”