AlGaN/GaN High-Electron-Mobility Transistor Using a Trench Structure for High-Voltage Switching Applications

Minki Kim,Ogyun Seok,Min-Woo Ha,Min-Koo Han

doi:10.5539/apr.v4n4p1

Minki Kim, Ogyun Seok + Show 2 more

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https://doi.org/10.5539/apr.v4n4p1

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Abstract

We proposed a new AlGaN/GaN high-electron-mobility transistor using a trench structure for high-voltage switching applications. The proposed trench structure was designed for the use at the gate edge, which improved the gate leakage current and breakdown voltage. We considered that the thickness of the AlGaN barrier was related to the polarization, surface-state density and leakage current. The surface states at the gate edge were controlled by etching the AlGaN barrier by 22 nm. The gate leakage current of the proposed device was 40 ?A/mm while that of a conventional device was 201 ?A/mm with a reverse gate-drain voltage of 100 V. The suppressed gate leakage current may have been caused by the decrease in the surface states at the gate edge. The breakdown voltage of the proposed device was 762 V while that of the conventional device without a trench structure was 120 V. The forward drain current and transconductance of the proposed device were decreased slightly because the channel resistance was increased in the trench region. The results of this study suggest that the trench structure improves the off-state characteristics of GaN power switches.

Highlights

GaN has been found to be a promising material for microwave and high-power applications due to its wide band gap, high critical field, and fast switching speed (Wu et al, 1996; Pearton et al, 1999)
If negative voltage is applied to the gate-drain of AlGaN/GaN HEMTs, the electrons can be trapped in the surface states from the gate (Vetury et al, 2001)
Σ+trench is less than σ+surface; the trench structure can suppress the leakage current by means of electron hopping in the surface states

Summary

Introduction

GaN has been found to be a promising material for microwave and high-power applications due to its wide band gap, high critical field, and fast switching speed (Wu et al, 1996; Pearton et al, 1999). A two-dimensional electron gas (Note 1) naturally forms between GaN and AlGaN by polarization. High mobility and high concentration at 2DEG have enabled a low on-resistance, a low power loss, and a high on-current of AlGaN/GaN high-electron-mobility transistors (Note 2) compared with Si MOSFETs (Ibbetson et al, 2000). The polarization induces surface states with shallow energy levels resulting from the charge neutrality. If negative voltage is applied to the gate-drain of AlGaN/GaN HEMTs, the electrons can be trapped in the surface states from the gate (Vetury et al, 2001). The trapping and hopping in the surface states induce leakage current, which decreases the breakdown voltage (Kim et al, 2005). It is necessary to suppress the surface leakage current for high-voltage switching operations

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