Suppression of High Threshold Voltage for Boron-Doped Diamond MOSFETs

Suppression of high threshold voltage (
${V} _{\text {TH}}$
) for the boron-doped diamond (B-diamond) MOSFETs plays a key role to design the diamond complementary MOS circuits with low gate drive sources. The
${V} _{\text {TH}}$
can be further suppressed by adjusting B-diamond epitaxial layer thickness, boron doping concentration, and gate oxide thickness. Three MOSFETs with different device structures are fabricated on the same oxygen-terminated B-diamond channel. Thickness and acceptor concentration for the B-diamond epitaxial layer are approximately 800 nm and
$1.36\times 10^{{16}}$
cm−3, respectively. A 45 nm-thick Al2O3 is deposited as the gate oxide by an atomic layer deposition technique. Maximum drain currents and ON/OFF ratios for the B-diamond MOSFETs are in the range of
$-2.4\sim - 4.3\,\,\mu \text{A}$
/mm and greater than
$10^{{6}}$
, respectively. Their
${V} _{\text {TH}}$
values are lower than 3.4 V with the lowest one of 0.8 V.