Investigation of Ohmic Contact Resistance, Surface Resistance, and Channel Resistance for Hydrogen-Terminated Diamond MOSFETs

The ohmic contact resistance (
${R}_{C}$
), surface resistance (
${R}_{S}$
), and channel resistance (
${R}_{\text {CH}}$
) of hydrogen-terminated diamond (H-diamond) MOSFETs were investigated in this study. Planar-type and T-type H-diamond MOSFETs were employed to analyze them. Because no interspaces exist between the source–drain and gate electrodes for the T-type H-diamond MOSFETs, then
${R}_{S}$
is zero. Both planar-type and T-type MOSFETs show low leakage current densities and good operations. By considering the relationships between the total resistance (
${R}_{ \mathrm{\scriptscriptstyle ON}}$
) and 1/
$\vert $
gate voltage-threshold voltage
$\vert $
,
${R}_{C}$
and
${R}_{\text {CH}}$
for the T-type H-diamond MOSFET at a gate voltage of −10.0 V are determined to be 13.8 and 21.8
$\Omega \cdot $
mm, respectively. As
${R}_{C}$
for both MOSFETs is the same,
${R}_{S}$
and
${R}_{\text {CH}}$
for the planar-type H-diamond MOSFET are deduced to be 90.0 and 15.8
$\Omega \cdot $
mm, respectively.
${R}_{S}$
accounts for 75.3% of
${R}_{ \mathrm{\scriptscriptstyle ON}}$
for the planar-type H-diamond MOSFET, which is the main reason for its lower drain current and extrinsic transconductance than those of the T-type MOSFET. Although
${R}_{S}$
is suppressed for the T-type H-diamond MOSFET,
${R}_{C}$
occupies 38.8% of
${R}_{ \mathrm{\scriptscriptstyle ON}}$
. To further improve the performance of the H-diamond MOSFETs, it is important to eliminate
${R}_{S}$
and decrease
${R}_{C}$
to further improve the electrical properties of the H-diamond MOSFETs.