Device Characteristics of AlGaN/GaN HEMTs with p-GaN Cap Layer

Abstract

In this study, AlGaN/GaN high-electron-mobility transistors with a 5-nm p-GaN cap layer were investigated to compare their performance under various activation conditions. Specifically, p-GaN cap layers were activated using rapid thermal annealing at 700°C for 5, 10, and 15 min in an N2 environment before device fabrication. The gate leakage current reduced considerably when the p-GaN cap layer activation time was longer. The measured on/off current ratio was improved to 9 × 107 for a Schottky-gate device with 15-min annealing time. The breakdown voltage was increased using the activated p-GaN cap layer. In pulsed I–V measurements, the device with the p-GaN cap layer with a 15-min activation time exhibited less current dispersion.

An AlGaN-GaN HEMT with p-GaN Extended Gate for Improvements on Current Dispersion and Breakdown Characteristics

“…Introducing a not fully depleted p-doped GaN cap improved the current collapse by screening the HEMT channel from surface potential fluctuations. 40,41 Since defects are the same for both devices in bulk, measuring gate lag directly assesses the variance in the p-GaN extension.…”

Characterization of AlGaN/GaN based HEMT for low noise and high frequency application

“…A thin i-GaN cap layer is usually used to prevent oxidation and damage to the AlGaN barrier layer and maintain polarization for 2DEG purposes. 25 However, authors in Arulkumaran et al 26…”

“…A thin i‐GaN cap layer is usually used to prevent oxidation and damage to the AlGaN barrier layer and maintain polarization for 2DEG purposes 25 . However, authors in Arulkumaran et al 26 demonstrated (with measurement results obtained from their fabricated HEMTs) that their HEMTs with n‐GaN cap layer exhibited good μ (mobility of electrons in 2DEG), g m (transconductance) and I Dmax (maximum drain current) values.…”

An analytical model for the current voltage characteristics of GaN-capped AlGaN/GaN and AlInN/GaN HEMTs including thermal and self-heating effects

“…The ohmic contact performance on GaN capped AlGaN/AlN/GaN HEMTs was improved by Wang et al [16] by optimizing the Ti/Al/Mo/Au electrodes. Finally, activated p-GaN cap layers have been demonstrated to increase the breakdown characteristics and reduce the leakage current of AlGaN/GaN HEMTs [17].…”