Thickness Effect on Operational Modes of ZnGa2O4 MOSFETs

The device mechanism from depletion to enhancement mode for ZnGa
₂
O
₄
metal-oxide semiconductor field effect transistors (MOSFETs) grown on the sapphire substrate by metalorganic chemical-vapor deposition was studied. It was found that the thickness of the ZnGa
₂
O
₄
thin-film would affect the operational mode of the MOSFETs. Under the low-voltage operation (V
_DS
= 0.5 V), the transistors exhibited a high on/off ratio from 10
⁷
to 10
⁴
, low subthreshold swing from 150 to 330 mV/dec, high field-effect mobility from 4.2 to 0.054 cm
²
/V-s and threshold voltages from -17.8 to 4.1 V (using constant current = 1 nA). These electrical properties all depend on the thickness of the ZnGa
₂
O
₄
thin-film transistors. Finally, the e-mode ZnGa
₂
O
₄
thin-film transistor with off-state breakdown voltage over 400 V is fabricated.