High breakdown voltage quasi-two-dimensional β-Ga₂O₃ field-effect transistors with a boron nitride field plate

We have demonstrated a β-Ga₂O₃ metal-semiconductor field-effect transistor (MESFET) with a high off-state breakdown voltage (344 V), based on a quasi-two-dimensional β-Ga₂O₃ field-plated with hexagonal boron nitride (h-BN). Both the β-Ga₂O₃ and h-BN were mechanically exfoliated from their respective crystal substrates, followed by dry-transfer onto a SiO₂/Si substrate for integration into a high breakdown voltage quasi-two-dimensional β-Ga₂O₃ MESFETs. N-type conducting behavior was observed in the fabricated β-Ga₂O₃ MESFETs, along with a high on/off current ratio (>10⁶) and excellent current saturation. A three-terminal off-state breakdown voltage of 344 V was obtained, with a threshold voltage of -7.3 V and a subthreshold swing of 84.6 mV/dec. The distribution of electric fields in the quasi-two-dimensional β-Ga₂O₃ MESFETs was simulated to analyze the role of the dielectric h-BN field plate in improving the off-state breakdown voltage. The stability of the field-plated β-Ga₂O₃ MESFET in air was confirmed after storing the MESFET in ambient air for one month. Our results pave the way for unlocking the full potential of β-Ga₂O₃ for use in a high-power nano-device with an ultrahigh breakdown voltage.