We demonstrate a passivated MESFET fabricated on (010) Si-doped β-Ga 2 O 3 with breakdown over 2.4 kV without field plates, high Power Figure of Merit (PFOM), and high estimated Huang's Material Figure of Merit (HMFOM), owing to low gate charge and high breakdown. MESFETs with 13 μm source-drain spacing and 75 nm channel exhibited a current density of 61 mA/mm, peak transconductance of 27 mS/mm, and on-resistance of 133 • mm. The device showed a PFOM competitive with state-of-theart β-Ga 2 O 3 devices and a record high estimated HMFOM for a β-Ga 2 O 3 device, competitive with commercial wide-band gap devices. This demonstrates high-performance β-Ga 2 O 3 devices as viable multi-kV high-voltage power switches.Index Terms-Field effect transistors, gallium oxide, MESFET, power transistors, ultra wide band gap semiconductors.
I. INTRODUCTIONβ -Ga 2 O 3 is an emerging ultra-wide band gap (UWBG) semiconductor that shows great promise in the highvoltage, high-power, and high-efficiency device space, particularly for power switching and switch-mode amplification [1], [2]. β-Ga 2 O 3 has a range of compatible shallow n-type dopants, including Sn, Si, and Ge [3], allowing for tunable carrier densities from 10 15 cm −3 to >10 20 cm −3 [4], [5] enabling a wide range of breakdown voltages V bk with low on resistance R on . The material has a high critical electric field strength E c estimated at 8 MV/cm due to its wide band Manuscript
We demonstrated 500 °C operation of field-effect transistors made using ultra-wide bandgap semiconductor β-Ga2O3. Metal–semiconductor field-effect transistors were fabricated using epitaxial conductive films grown on an insulating β-Ga2O3 substrate, TiW refractory metal gates, and Si-implanted source/drain contacts. Devices were characterized in DC mode at different temperatures up to 500 °C in vacuum. These variable-temperature measurements showed a reduction in gate modulation of the drain current due to an increase in gate leakage across the gate/semiconductor Schottky barrier. Devices exhibited a reduction in transconductance with increasing temperature; despite this, drain current increased with temperature due to a reduction in threshold voltage caused by the de-trapping of electrons from deep-level traps. Devices also showed negligible change in semiconductor epitaxy and source/drain contacts, hence demonstrated recovery to their room-temperature electrical properties after the devices were tested intermittently at different high temperatures in vacuum. The mechanism of gate leakage was also explored, which implicated the presence of different conduction mechanisms at different temperatures and gate electric fields.
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