Deep traps localization in AlGaN/GaN MIS-HEMTs by a comparative study using capacitance and current deep level transient spectroscopies

Mariam El-Khatib,Georges Bremond,Erwan Morvan,Gérard Guillot,Philippe Ferrandis

doi:10.1088/1742-6596/1190/1/012013

Abstract

In this study, deep traps in multiple-finger normally-off AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) were identified. The localization of these traps has been established by a comparative study using capacitance and current deep level transient spectroscopies (DLTS). The Cgd-DLTS measurements cover the GaN buffer region between the gate and drain contacts. On the other hand, the IDS-DLTS measurements cover the channel region in GaN including the zone under the gate. Two electron traps, E2 (0.31eV) and E4 (0.5eV) have been detected. They are respectively attributed to reactive ion etching (RIE) induced surface damage. These two traps are more likely located in the GaN channel close to the gate. Two other deep electron traps E5 (0.64eV) and E6 (0.79eV) have also been detected and are localized in the GaN buffer layer.

Highlights

GaN material holds an advantageous position in the fabrication of power devices [1]
Electrical characteristics and deep level transient spectroscopy data were acquired with a Fourier transform deep level transient spectroscopy (FT-DLTS) system from PhysTech (FT 1030) using a Boonton 72B capacitance meter with a 100mV test signal at 1MHz
This IDS-DLTS measurement covers the channel region in GaN including the zone under the gate, which can explain the dominance of the two defects E2 and E4 related to the gate etching process

Summary

Introduction

GaN material holds an advantageous position in the fabrication of power devices [1]. This advantage is manifested by the possibility to perform GaN based devices working in high voltage, high current, high frequency and high temperature conditions. Despite these theoretical forecasts, trapping mechanisms limit the performances of the GaN devices [2]. In this context, the deep level transient spectroscopy (DLTS) is one of the most well-adapted techniques for deep-level characterization. The deep levels in the MIS-HEMTs were examined and localized by comparing capacitance deep level transient spectroscopy (C-DLTS) and drain-source current DLTS (I-DLTS) applied directly on MIS-HEMT transistors

Experimental methods

Experiments and results

Conclusion