Reliable Ohmic Contact Properties for Ni/Hydrogen-Terminated Diamond at Annealing Temperature up to 900 °C

Xiaolu Yuan,Bo Da,Junjun Wei,Chengming Li,Jinlong Liu,Jiangwei Liu,Yasuo Koide

doi:10.3390/coatings11040470

Abstract

Ohmic contact with high thermal stability is essential to promote hydrogen-terminated diamond (H-diamond) electronic devices for high-temperature applications. Here, the ohmic contact characteristics of Ni/H-diamond at annealing temperatures up to 900 °C are investigated. The measured current–voltage curves and deduced specific contact resistance (ρC) are used to evaluate the quality of the contact properties. Schottky contacts are formed for the as-received and 300 °C-annealed Ni/H-diamonds. When the annealing temperature is increased to 500 °C, the ohmic contact properties are formed with the ρC of 1.5 × 10−3 Ω·cm2 for the Ni/H-diamond. As the annealing temperature rises to 900 °C, the ρC is determined to be as low as 6.0 × 10−5 Ω·cm2. It is believed that the formation of Ni-related carbides at the Ni/H-diamond interface promotes the decrease in ρC. The Ni metal is extremely promising to be used as the ohmic contact electrode for the H-diamond-based electronic devices at temperature up to 900 °C.

Highlights

The Ti metal used as key-patterns was deposited on the H-diamond by a J-sputter system in an Ar atmosphere in order to align the positions of the mesa structure and contact metals
The electrical properties of Ni/H-diamond contacts were characterized by a room-temperature probe system
All the Ni metals were stable to be formed on the H-diamond

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. With many remarkable intrinsic properties, possesses vast prospect applications for high-power, high-frequency, and high-temperature electronics [1,2,3]. It exhibits an ultrawide energy bandgap (5.5 eV), high carrier mobilities (4500 and 3800 cm2 ·V−1 ·s−1 for electrons and holes, respectively), large breakdown field strength (10 MV·cm−1 ), and the highest thermal conductivity (22 W cm−1 ·K−1 ) [4]. [12,13,14,15] They show good ohmic contact properties and high thermal stability, with annealing temperatures up to 700 ◦ C. The measured current–voltage curves and deduced specific contact resistance (ρC ) are used to evaluate the quality of the contact properties

Preparation of H-Diamond Epitaxial Layer

Annealing Process and Current–Voltage Measurements

Results and Discussion

Conclusions