Mobility Enhancement in RF-Sputtered MgZnO/ZnO Heterostructure Thin-Film Transistors

Coplanar top-gate MgZnO/ZnO heterostructure thin-film transistors (TFTs) are fabricated on glass substrates using a large-area processing compatible RF-sputtering technique. The field-effect mobility increases with the Mg content in the MgZnO capping layer. The threshold voltage, saturation field-effect mobility, and ON/OFF current ratio of an Mg
_0.2
Zn
_0.8
O/ZnO heterostructure TFT are -0.55 V, 84.22 cm
²
V
^-1
s
^-1
, and 3 × 10
⁶
, respectively. In comparison with a ZnO TFT, the mobility is enhanced by a factor of >50. Inverters based on Mg
_0.2
Zn
_0.8
O/ZnO TFTs are then demonstrated by connecting load transistors operated at VGS = VDD (supply voltage) to drive transistors. A peak gain magnitude of 19.6 is obtained in the Mg
_0.2
Zn
_0.8
O/ZnO inverter with a geometric aspect ratio of 15 at VDD of 18 V.