High Output Power Density of 2DHG Diamond MOSFETs With Thick ALD-Al<sub>2</sub>O<sub>3</sub>
Ken Kudara, Shoichiro Imanishi, Atsushi Hiraiwa, Yuji Komatsuzaki, Yutaro Yamaguchi, Yoshifumi Kawamura, Shintaro Shinjo, Hiroshi Kawarada
Abstract
This article reports on the high operation voltage large-signal performance of two-dimensional hole gas diamond metal-oxide semiconductor field-effect transistors (MOSFETs) with thick atomic-layer-deposition (ALD)-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> formed on high purity polycrystalline diamond with a (110) preferential orientation. MOSFETs with a 1- μm gate-length having a gate oxide layer of 200-nm-thick Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , formed by ALD and asymmetric structures, to withstand high-voltage operations. The large-signal performances were evaluated at a quiescent drain voltage of greater than -60 V for the first time in diamond field-effect transistor (FET). As a result, an output power density of 2.5 W/mm under class-A operation at 1 GHz, which is higher than that of diamond FETs fabricated by a self-aligned gate process, was obtained. Moreover, an output power density of 1.5 W/mm was exhibited by the MOSFET when biased at a quiescent drain voltage of -40 V under class-AB operation at 3.6 GHz using an active load-pull system. This is the highest recorded value for diamond FETs at a frequency greater than 2 GHz, owing to the high-voltage operation. These results indicate that diamond p-FETs under high-voltage operations are the most suitable for high-power amplifiers with complementary circuits.