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.