Influence factors and temperature reliability of ohmic contact on AlGaN/GaN HEMTs

Liang Song,Ronghui Hao,Guohao Yu,Jie Zhao,Baoshun Zhang,Xiaodong Zhang,Yaming Fan,Yong Cai,Fu Chen,Kai Fu

doi:10.1063/1.5024803

Abstract

In this paper, we have studied the performance of Ti/Al/Ni/Au ohmic contact with different Al and Au thicknesses and pretreatments. The temperature dependence of contact resistances (Rc) was investigated and it shows that there are different optimal annealing temperatures with different metal thicknesses and pretreatments. The optimal annealing temperature is affected by Al and Au thickness and AlGaN thickness. The etched AlGaN barrier is useful to achieve good ohmic contact (0.24 Ω·mm) with a low annealing temperature. Only the contact resistances of the samples with 130 nm Al layer kept stable and the contact resistances of the samples with 100nm and 160 nm Al layers increased with the measurement temperatures. The contact resistances showed a similar increase and then keep stable trend for all the samples in the long-term 400 °C aging process. The ohmic metal of 20/130/50/50 nm Ti/Al/Ni/Au with ICP etching is the superior candidate considering the contact resistance and reliability.

Highlights

AlGaN/GaN high electron mobility transistors (HEMTs) are excellent candidates for high power applications at microwave frequencies and high-temperature electronic field, owing to the high electron velocity, high critical electric field and high density two-dimensional electron gas (2DEG).[1,2,3,4]
The formation of ohmic contacts with low contact resistance is extremely crucial in order to achieve high-frequency performance of AlGaN/GaN HEMTs
Shinohara et al.[6] reported record DC and RF performance obtained in deeply-scaled selfaligned-gate GaN-HEMTs with heavily-doped n+-GaN ohmic contacts to two-dimensional electron gas (2DEG)

Summary

Introduction

AlGaN/GaN high electron mobility transistors (HEMTs) are excellent candidates for high power applications at microwave frequencies and high-temperature electronic field, owing to the high electron velocity, high critical electric field and high density two-dimensional electron gas (2DEG).[1,2,3,4]. It can be seen that the ohmic properties for sample A was obtained after annealing at a temperature as low as 810 ◦C, but the contact resistance is still high.

Results

Conclusion