Comprehensive Schottky Barrier Height Behavior and Reliability Instability with Ni/Au and Pt/Ti/Pt/Au on AlGaN/GaN High-Electron-Mobility Transistors.

Tae-Woo Kim,Surajit Chakraborty

doi:10.3390/mi13010084

Abstract

The reliability instability of inhomogeneous Schottky contact behaviors of Ni/Au and Pt/Ti/Pt/Au gate contacts on AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated via off-state stress and temperature. Under the off-state stress condition, Pt/Ti/Pt/Au HEMT showed abruptly reduced reverse leakage current, which improved the Schottky barrier height (SBH) from 0.46 to 0.69 eV by suppression of the interfacial donor state. As the temperature increased, the reverse leakage current of the Pt/Ti/Pt/Au AlGaN/GaN HEMT at 308 K showed more reduction under the same off-state stress condition while that of the Ni/Au AlGaN/GaN HEMT increased. However, with temperatures exceeding 308 K under the same off-state stress conditions, the reverse leakage current of the Pt/Ti/Pt/Au AlGaN/GaN HEMT increases, which can be intensified using the inverse piezoelectric effect. Based on this phenomenon, the present work reveals the necessity for analyzing the concurrent SBH and reliability instability due to the interfacial trap states of the MS contacts.

Highlights

Gallium nitride (GaN)-based high-electron-mobility transistors (HEMTs) have attracted attention in microwave and power-switching applications due to their unparalleled properties including wide direct bandgap, high-temperature operation, high breakdown field, and high-saturation electron velocity [1,2,3]
The present work reveals the necessity for analyzing the concurrent SBH and reliability instability due to the interfacial trap states of the Keywords: AlGaN/GaN; critical voltage; degradation; off-state stress; inverse piezoelectric effect; high temperature; Schottky barrier height; reliability instability
The SBH of the Pt/Ti/Pt/Au process on the AlGaN/GaN HEMTs caused cracks in the MS contacts. This phecontact at the reverse-biased region was observed to deteriorate, implying that the surface nomenon can be attributed to the inhomogeneities at the MS interface and large deviations roughness caused by the high-energy Pt atoms deposited during e-beam evaporation proin the behaviors of the top electrodes despite the higher work function of Pt compared with cess on the AlGaN/GaN HEMTs caused cracks in the MS contacts

Summary

Introduction

Gallium nitride (GaN)-based high-electron-mobility transistors (HEMTs) have attracted attention in microwave and power-switching applications due to their unparalleled properties including wide direct bandgap, high-temperature operation, high breakdown field, and high-saturation electron velocity [1,2,3]. The gate reverse leakage current still remains a key concern for GaN-HEMT stability due to the interfacial trap states and strain-induced defects such as dislocations and cracks from large lattice mismatches [8,9,10,11,12]. Severe limitations such as current collapse, power slump, and poor long-term reliability are induced by the trapping effects at the interfacial trap states, trap sites in the AlGaN barrier layer, and deep-level traps in the GaN buffer layer [13,14,15]. There are many studies [26,27,28,29,30,31] on the reliability of the Ni and Pt gated structure, but our experimental method is unique and revived the property of Pt metal into its original condition

Materials and Methods

Impact

C–V Method

Reliability Instability Based on Temperature

Conclusions