Transport Properties of the Two-Dimensional Hole Gas for H-Terminated Diamond with an Al2O3 Passivation Layer

Cui Yu,Aimin Bu,Jianchao Guo,Chuangjie Zhou,Mengyu Ma,Hongxing Wang,Zhihong Feng,Zezhao He

doi:10.3390/cryst12030390

Abstract

Diamonds are thought to be excellent candidates of next-generation semiconductor materials for high power and high frequency devices. A two-dimensional hole gas in a hydrogen-terminated diamond shows promising properties for microwave power devices. However, high sheet resistance and low carrier mobility are still limiting factors for the performance improvement of hydrogen-terminated diamond field effect transistors. In this work, the carrier scattering mechanisms of a two-dimensional hole gas in a hydrogen-terminated diamond are studied. Surface roughness scattering and ionic impurity scattering are found to be the dominant scattering sources. Impurity scattering enhancement was found for the samples after a high-temperature Al2O3 deposition process. This work gives some insight into the carrier transport of hydrogen-terminated diamonds and should be helpful for the development of diamond field effect transistors.

Highlights

Due to its high critical breakdown electric field, high carrier saturation drift velocity, high thermal conductivity, and high carrier mobility, diamonds have great application potential in high power and high frequency areas [1]
A hydrogen-terminated (H-terminated) diamond surface demonstrates a relatively high surface conductivity due to the forming of a two-dimensional hole gas (2DHG) by transfer doping from adsorbates/dielectric materials in contact with a H-terminated diamond surface
For high power and high frequency applications, the sheet resistance of the 2DHG is still at a high level and the carrier mobility is low, which leads to large parasitic resistance and limits the performance of H-terminated diamond field effect transistors (FETs)

Summary

Introduction

Due to its high critical breakdown electric field, high carrier saturation drift velocity, high thermal conductivity, and high carrier mobility, diamonds have great application potential in high power and high frequency areas [1]. A hydrogen-terminated (H-terminated) diamond surface demonstrates a relatively high surface conductivity due to the forming of a two-dimensional hole gas (2DHG) by transfer doping from adsorbates/dielectric materials in contact with a H-terminated diamond surface. H-terminated diamond field effect transistors (FETs) have obtained good direct current (DC) and radio frequency (RF) performances. 1.3 A/mm [7] and a maximum oscillation frequency (f max ) of 120 GHz [8] have been obtained for H-diamond FETs. Recently, the output power density was improved and reached 3.8 W/mm at 1 GHz [9]. The surface adsorbates would be broken during the high temperature process, which influences the electrical properties of the 2DHG of the H-terminated diamond

Methods

Results

Conclusion