Microwave TFTs Made of MOCVD ZnO With ALD Al2O3 Gate Dielectric

In this paper, we report on the demonstration of microwave ZnO thin-film transistors (TFTs) grown by metal organic chemical vapor deposition (MOCVD) on a SiO
₂
/Si substrate. In order to realize the microwave performance ZnO TFTs grown by MOCVD, the inverted staggered type device structure and the high quality Al
₂
O
₃
gate dielectric layer grown by atomic layer deposition were employed. ZnO TFTs show the depletion mode operation and exhibit an on/off drain current ratio of 6.7 × 10
⁶
, a peak transconductance of 124 μS, and a field-effect mobility (μFE) of 23.3 cm
²
/V·s, respectively. As a result of excellent dc performance, a cut-off frequency (f
_T
) of 0.73 GHz and a maximum oscillation frequency (f
_max
) of 2 GHz were achieved.