HfAlOx/Al2O3 Bilayer Dielectrics for a Field Effect Transistor on a Hydrogen-Terminated Diamond.

Minghui Zhang,Yanfeng Wang,Wei Wang,Shi He,Genqiang Chen,Renan Bu,Feng Wen,Shuwei Fan,Fang Lin,Hongxing Wang

doi:10.3390/ma15020446

Abstract

In this work, a hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with HfAlOx/Al2O3 bilayer dielectrics is fabricated and characterized. The HfAlOx/Al2O3 bilayer dielectrics are deposited by the atomic layer deposition (ALD) technique, which can protect the H-terminated diamond two-dimensional hole gas (2DHG) channel. The device demonstrates normally-on characteristics, whose threshold voltage (VTH) is 8.3 V. The maximum drain source current density (IDSmax), transconductance (Gm), capacitance (COX) and carrier density (ρ) are −6.3 mA/mm, 0.73 mS/mm, 0.22 μF/cm2 and 1.53 × 1013 cm−2, respectively.

Highlights

The diamond is considered as an ultimate semiconductor with ultrawide bandgap of 5.47 eV, extremely high breakdown field of 10 MV/cm, highest thermal conductivity of 22 W/cm·K, high carrier mobility and large carrier saturation velocity [1,2,3,4]
This technique requires the precise control of the doping thickness, and the carrier mobility is not ideal [5]
We study a H-terminated diamond field effect transistor (FET) with HfAlOx/Al2O3 bilayer dielectrics, and its electrical properties were evaluated by semiconductor analyzer

Summary

Introduction

The diamond is considered as an ultimate semiconductor with ultrawide bandgap of 5.47 eV, extremely high breakdown field of 10 MV/cm, highest thermal conductivity of 22 W/cm·K, high carrier mobility (electrons of 4500 cm2/V·s, holes of 3800 cm2/V·s) and large carrier saturation velocity (electrons of 1.5–2.7 × 107 cm/s, holes of 0.85–1.2 × 107 cm/s) [1,2,3,4]. Since the dopants cannot be activated at room temperature with high activation energy (boron of 370 meV and phosphorous of 650 meV) [5], the application of diamonds has been greatly hindered. In this case, δ-doping comes into being. The dielectric material with high dielectric constant can control large charge responses at a small bias effectively [14]. Many high dielectric constant materials have been employed for the fabrication of a H-terminated diamond FET [10,15].

Materials and Methods

Gate Materials

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