Anisotropic Electron Mobility and Contact Resistance of β-Ga<sub>2</sub>O<sub>3</sub> Obtained via Radio Frequency Transmission Line Methods on Schottky Devices
Hyunjung Kim, Sungjae Hong, Chorom Jang, Hye‐Jin Jin, H.‐G. WOO, Heesun Bae, Seongil Im
Abstract
Monoclinic semiconducting β-Ga 2 O 3 has drawn attention, particularly because its thin film could be achieved via mechanical exfoliation from bulk crystals, which is analogous to van der Waals materials’ behavior. For the transistor devices with exfoliated β-Ga 2 O 3, the channel direction becomes [010] for in-plane electron transport, which changes to vertical [100] near the source/drain (S/D) contact. Hence, anisotropic transport behavior is certainly worth to study but rarely reported. Here we achieve the vertical [100] direction electron mobility of 4.18 cm 2 /(V s) from Pt/β-Ga 2 O 3 Schottky diodes with various thickness via radio frequency-transmission line method (RF-TLM), which is recently developed. The specific contact resistivity (ρ c ) could also be estimated from RF-TLM, to be 4.72 × 10 –5 Ω cm 2, which is quite similar to the value (5.25 × 10 –5 Ω cm 2 ) from conventional TLM proving the validity of RF-TLM. We also fabricate metal–semiconductor field-effect transistors (MESFETs) to study anisotropic transport behavior and contact resistance ( R C ). R C -free [010] in-plane mobility appears as high as maximum ∼67 cm 2 /(V s), extracted from total resistance in MESFETs.