Improved Stability of High-Performance ZnO/ZnMgO Hetero-MISFETs

Improved performance and stability was demonstrated for ZnO/ZnMgO hetero-MISFETs. The MIS gate structures that were formed using either a 50-nm-thick Al
₂
O
₃
or HfO
₂
gate dielectric layer were examined by observation of the transfer characteristic hysteresis. A significantly reduced hysteresis of less than 0.1 V was obtained for HfO
₂
as compared to that for the Al
₂
O
₃
gate dielectric. By reducing the access resistance, the 1-mum gate devices showed improved transconductance values, as high as 54 mS/mm for Al
₂
O
₃
and 71 mS/mm for HfO
₂
, which are the highest values ever reported for ZnO-based FETs.