Quasi-Two-Dimensional β-Ga2O3 based Hetero-Structure Transistors

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β-Ga2O3 is a wide band gap (4.8 eV) semiconducting material with outstanding chemical and thermal stabilities. As the breakdown voltage of β-Ga2O3 is estimated to be as high as 8 MV/cm, it can be applied to high-power electronics. After β-Ga2O3 thin layers were successfully exfoliated from bulk single crystals by mechanical exfoliation method, the study of high power 2D nano-electronics using β-Ga2O3 received a considerable attention. Though β-Ga2O3 is not a two-dimensional Van der Waals material like graphene and MoS2, a bulk β-Ga2O3 crystal can be easily cleaved into thin nano-flakes in the (100) direction; it has monoclinic structure and the lattice constant is larger along the cleaved plane. Moreover, this ultrathin β-Ga2O3 flakes can be integrated with other 2D materials such as hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDs) to make down-scaled, flexible devices. We demonstrated two types of heterostructure devices (MISFETs and JFETs) based on β-Ga2O3 flakes and 2D materials using PDMS stamp method and photolithography. β-Ga2O3/h-BN hetero-structure based quasi-two-dimensional metal insulator semiconductor field-effect transistors(MISFETs) are fabricated. The h-BN dielectric, which has an extraordinarily flat and clean surface, provides a minimal density of charged impurities at the interface between β-Ga2O3 and h-BN, resulting in excellent device performances. The fabricated MISFETs showed superior drain current modulation with high on/off ratio and low gate leakage current. The double-gating of the fabricated device was demonstrated by biasing both top and bottom gates, achieving the modulation of the threshold voltage. N-channel β-Ga2O3/WSe2 heterostructure junction field effect transistors (JFETs) are demonstrated with good gate modulation and negligible hysteresis. Tungsten diselenide (WSe2) is mostly known as a stable p-type 2D layered material. The fabricated heterostructure JFETs also showed excellent ambient stability. The successful JFET operation is attributed to Van der Waals junction interface between β-Ga2O3 and WSe2. These heterostructured wide-band-gap nanodevices show a new route toward stable and high-power nanoelectronic devices. The details of the fabrication procedure and results will be presented.