145-MW/cm2 Heteroepitaxial Diamond MOSFETs With NO2 p-Type Doping and an Al2O3 Passivation Layer

In this study, we investigated diamond metal oxide semiconductor field effect transistors (MOSFETs) with NO₂ p-type doping and Al₂O₃ passivation layer fabricated on a high-quality heteroepitaxial single crystal (001) diamond substrate called Kenzan diamond^®. MOSFETs with a gate length of 1.4 $\mu \text{m}$ and nearly zero source-gate spacing exhibited a high drain current density of −776 mA/mm with a negligible gate leakage current ( $< 0.1~\mu \text{A}$ /mm). MOSFETs with a gate-to-drain length of 4.8 $\mu \text{m}$ delivered a high off-state breakdown voltage (−618 V) at an average breakdown field of 1.2 MV/cm and a specific on-resistance of 2.63 $\text{m}\Omega \cdot $ cm². Baliga’s Figure-Of-Merits was calculated as 145 MW/cm² and the anticipated maximum power density was 12 W/mm. The diamond MOSFET was improved with high crystal quality.

I. Introduction

Diamond is known for its excellent electronic and thermal properties, such as high band gap energy (5.47 eV), breakdown field (>10 MV/cm), [1], [2] and high thermal conductivity (22 W/Kcm) [3]. These exceptional properties enable diamond to offer highly efficient and high-power device properties compared with SiC and GaN. Moreover, diamond has high electron and hole mobilities (4500 and 3800 cm²/Vs, respectively) [4], which are preferred for high radio frequency (RF) power devices. Diamond field effect transistors (FETs) showed an excellent RF output power density of 2.1 W/mm at 1 GHz [5], a cut-off frequency () of 70 GHz [6], and a maximum frequency of oscillation () of 120 GHz [7].