Lateral α-Ga2O3:Zr metal–semiconductor field effect transistors

We present α-Ga2O3:Zr based metal–semiconductor field-effect transistors (MESFETs) with PtOx/Pt gate contacts. Pulsed laser deposition is used to grow the α-Ga2O3:Zr thin films in a two-step process on m-plane α-Al2O3. A nominally undoped α-Ga2O3 layer is grown at high growth temperature as growth template. Subsequently, a α-Ga2O3:Zr layer is grown at a lower growth temperature. We compare the performance of Ring-FET devices on a planar 30 nm thick zirconium doped layer deposited at 465 °C and mesa-FETs on a 35 nm thick thin film deposited at 500 °C. The Ring-FETs have current on/off ratios as high as 1.7×109 and a threshold voltage of −0.28 V, and they exhibit very low mean sub-threshold swing of (110±20) mV/dec. For the mesa-FETs, smaller current on/off ratios of 4×107 are measured and a threshold voltage of −1.5 V was obtained due to the larger thin film thickness. The on/off ratio is limited by a higher tunneling current in the off-regime. We present high voltage measurements, which show a breakdown of the mesa-FET device at −340 V, corresponding to a high breakdown field of 1.36 MV/cm and significantly exceeding the previously achieved breakdown voltage for α-Ga2O3 based MESFETs.