Electrical Characteristics of H-Diamond Transistors With ZrO2/Zr Stacked Dielectrics Deposited by Electron Beam Evaporation

Enhancement mode diamond field-effect transistors with large threshold voltage and low leakage current are highly in demand for low-power electronics. In this article, hydrogen-terminated diamond (H-diamond) transistors with ZrO2/Zr stacked dielectrics deposited by electron beam (EB) evaporation were demonstrated. The threshold voltages boosted from −0.4 to −2.5 V with gate length increasing from 2 to $8~\mu \text{m}$ , indicating the normally- OFF operation. The OFF-state leakage current of 10−8 mA/mm and gate–source leakage current density of about $10^{-{7}}$ A/cm2 were acquired both for 6- and 8- $\mu \text{m}$ gate length devices. Additionally, the ON/OFF ratio and subthreshold swing (SS) for the device with a 6- $\mu \text{m}$ gate length were deduced to be $10^{{9}}$ and 128 mV/decade, respectively. The maximum drain current density increases with the gate length shortens and reaches up to −74 mA/mm for the device with a 2- $\mu \text{m}$ gate length. These performances suggest that the EB method is applicable to fabricate the ZrO2/Zr gate for realizing normally- OFF H-diamond FETs.