Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

Xiaoqing Xu,Aras Norvilas,Hongyun So,Jiebin Zhong,Debbie G Senesky,Christof Sommerhalter,Mary Tang

doi:10.1063/1.4967816

Abstract

In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG) properties of AlGaN/GaN high electron mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition (MOCVD) on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72%) across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/V⋅s at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/V⋅s which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

Highlights

One of the most important applications is in the fabrication of AlGaN/GaN high electron mobility transistor (HEMT) which utilizes a two-dimensional electron gas (2DEG) layer formed at the interface of GaN and AlGaN
We focus on three aspects: 1. The uniformity of 2DEG mobility across 4-inch wafer, which is a combined effect of Al% and thickness distributions of the AlGaN barrier, AlN spacer and GaN cap thickness distributions, and C% distribution in the GaN layer, all closely related with the growth temperature and its distribution; 2
The Al% distribution is a good indicator of the growth temperature distribution, the uniformity of 2DEG performance can be tuned by the uniformity of Al% in the AlGaN barrier

Summary

Introduction

The high growth quality and high throughput capabilities of metal-organic chemical vapor deposition (MOCVD) have enhanced and propelled research of III-nitride in power electronics, optoelectronics, timing references, high frequency applications, and harsh environment sensors.[1,2,3,4,5,6,7,8,9,10,11] One of the most important applications is in the fabrication of AlGaN/GaN high electron mobility transistor (HEMT) which utilizes a two-dimensional electron gas (2DEG) layer formed at the interface of GaN and AlGaN. The main factors influencing AlGaN/GaN 2DEG concentration and mobility are: Al% in the AlGaN barrier,[12,13,14] AlGaN barrier thickness,[12,13,14] AlN spacer thickness,[12,13] GaN cap thickness,[15] and the impurity level[16,17,18] especially C% in the GaN layer, all dependent on the growth temperature and its distribution. The uniformity of 2DEG mobility across 4-inch wafer, which is a combined effect of Al% and thickness distributions of the AlGaN barrier, AlN spacer and GaN cap thickness distributions, and C% distribution in the GaN layer, all closely related with the growth temperature and its distribution; 2.

Methods

Results

Conclusion