Nanomembrane β-Ga2O3 high-voltage field effect transistors

There is considerable excitement recently in the field of transparent conducting-oxide-semiconductors due to the successful realization of large-area single crystals of the wide-bandgap semiconductor β-Ga₂O₃ by bulk growth methods [1]. The availability of bulk β-Ga₂O₃ crystals led to the rapid demonstration of high-voltage metal-semiconductor field-effect transistors (MESFETs) by controlled Sn-doped epilayers grown by molecular beam epitaxy (MBE) [2]. β-Ga₂O₃ has an energy bandgap of ~4.9 eV, significantly larger than both GaN and SiC. Coupled with the availability of low-cost bulk crystals, this material is highly attractive for high-voltage switching applications. Here we show preliminary results that show that similar to layered crystals [3] and rather surprisingly, one can peel-off nanoscale layers of β-Ga₂O₃ from a nominally undoped bulk single-crystal. Conducting channels can then be created electrostatically in these nanomembranes with a back-gate, and the resulting transistors are able to sustain very high voltages and still switch by several orders of magnitude.