Comparative study of Au and Ni/Au gated AlGaN/GaN high electron mobility transistors

Manoj Saxena,Chandan Sharma,Seema Vinayak,Sonalee Kapoor,Robert Laishram,D S Rawal,Ajay Kumar Visvkarma

doi:10.1063/1.5116356

Abstract

This paper presents the electrical comparison of Au and Ni/Au gated HEMT devices and diodes. Au Schottky diodes on an AlGaN/GaN heterostructure exhibit better electrical performance in comparison to conventional Ni/Au diodes with an improved Schottky barrier height (SBH) and lower reverse leakage current. The SBH extracted from I-V for Au and Ni/Au is 1.29 eV and 0.74 eV, respectively. Au Schottky contacts on GaN have a better ideality factor of 1.55 than Ni, which is 1.61. Capacitance-voltage measurement revealed a positive shift in threshold voltage in the case of Au diodes with a reduced capacitance value with respect to Ni/Au diodes. This decrease in threshold and capacitance indicates a decrease in the 2DEG carrier concentration. The decrease in the 2DEG carrier concentration is consistent with three terminal device measurements. Despite a small decrease in drain current (8%), the Au gated HEMT devices have shown an improved subthreshold slope (13%) and nearly 4 order improvement in the ION/IOFF ratio than Ni/Au gated HEMTs. Pulse IV characterization has indicated that gate lag and drain lag have no major changes with respect to gate metal, whereas current collapse increases for high work function metals.

Highlights

Wide bandgap III–V semiconductor materials like gallium nitride (GaN) and its doped family members (AlGaN/InGaN) possess incredible material properties like high and direct bandgap, high thermal conductivity, and high breakdown electric field in comparison to conventional semiconductors like silicon and gallium arsenide (GaAs)
Au and Ni/Au gated HEMT devices were fabricated on an AlGaN/GaN HEMT epistructure
The Capacitance voltage (CV) reveals better gate characteristics of the Au Schottky contact in comparison to Ni/Au Schottky contacts with a lower threshold value of ΔV = 0.39 V and with almost the same gate capacitance. This shift in threshold with Au gated GaN HEMT devices is positive in nature, shifting them toward enhancement mode devices

Summary

Introduction

Wide bandgap III–V semiconductor materials like gallium nitride (GaN) and its doped family members (AlGaN/InGaN) possess incredible material properties like high and direct bandgap, high thermal conductivity, and high breakdown electric field in comparison to conventional semiconductors like silicon and gallium arsenide (GaAs). The performance of GaN-HEMT devices is a strong function of both ohmic and Schottky metal contacts.

Results

Conclusion