Ambipolar Channel p-TMD/n-Ga<sub>2</sub> O<sub>3</sub> Junction Field Effect Transistors and High Speed Photo-sensing in TMD Channel.

Choi, Wonjun; Ahn, Jongtae; Kim, Ki-Tae; Jin, Hye-Jin; Hong, Sungjae; Hwang, Do Kyung; Im, Seongil · Adv Mater · 2021

basic_science · Level V

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Abstract

Highly crystalline 2D/3D-mixed p-transition metal dichalcogenide (TMD)/n-Ga<sub>2</sub> O<sub>3</sub> heterojunction devices are fabricated by mechanical exfoliation of each p- and n-type material. N-type β-Ga<sub>2</sub> O<sub>3</sub> and p-type TMD separately play as a channel for junction field effect transistors (JFETs) with each type of carriers as well as materials for a heterojunction PN diode. The work thus mainly focuses on such ambipolar channel transistors with two different types of channel in a single device architecture. For more extended applications, the transparency of high energy band gap β-Ga<sub>2</sub> O<sub>3</sub> (E<sub>g</sub>  ≈ 4.8 eV) is taken advantage of, firstly to measure the electrical energy gap of p-TMDs receiving visible or near infrared (NIR) photons through the β-Ga<sub>2</sub> O<sub>3</sub> . Next, the p-TMD/n-Ga<sub>2</sub> O<sub>3</sub> JFETs are put to high speed photo-sensing which is achieved from the p-TMD channel under reverse bias voltages on n-Ga<sub>2</sub> O<sub>3</sub> . The photo-switching cutoff frequency appears to be ≈16 and 29 kHz for visible red and NIR illuminations, respectively, on the basis of -3 dB photoelectric power loss. Such a high switching speed of the JFET is attributed to the fast transport of photo-carriers in TMD channels. The 2D/3D-mixed ambipolar channel JFETs and their photo-sensing applications are regarded novel, promising, and practically easy to achieve.