Simulation of β - Ga2O3 based MOSFETs for Depletion and Enhancement Mode Operation

This paper reports on TCAD-simulation of beta-gallium oxide ( β - Ga 2 O 3 ) MOSFET with the channel recessed into a 1 µ m thick Si-doped (1 × 10 18 cm - 3) epitaxial layer. We optimized gate recess thickness to achieve both, depletion and enhancement mode operation. The simulated β - Ga2O3 MOSFET structures show optimum depletion-mode and enhancement-mode characteristics for 150 nm and 15 nm active channel thickness, respectively. A comparative study is also done to analyze the thermal and electrical effects by simulating hetero-epitaxial β - Ga 2O3 layer on sapphire substrate and homoepitaxial β - Ga2O3 layer on β - Ga 2 O 3 substrate. MOSFET devices based on β - Ga 2 O 3 layers on sapphire substrates show improved performance compared to devices based on β - Ga2O3 layers on β - Ga 2 O 3 substrates in terms of drain current, trans-conductance and breakdown voltage. β - Ga 2 O 3 epitaxial layers on sapphire substrates exhibit a drain current density of 77.7 mA/mm with a peak trans-conductance of 2.28 mS/mm for D-mode operation and 27.3 mA/mm drain current density with a peak trans-conductance of 3.92 mS/mm for E-mode operation. In contrast, MOSFET devices based on β - Ga 2 O 3 epitaxial layers on β - Ga 2 O 3 substrates show a drain current density of 64.1 mA/mm for D-mode operation and 22.2 mA/mm drain current density with 3.2 mS/mm peak trans-conductance for E-mode operation. MOSFET devices based on β - Ga 2 O 3 epitaxial structures on sapphire and on β - Ga 2 O 3 substrates show reliable switching properties with sub-threshold swing of 95.98 mV/dec and 87.05 mV/dec respectively as well as a high I on =I off ratio of 10 11 . These simulation results show potential of laterally scaled β - Ga 2 O 3 MOSFETs for power switching applications.