RF and Logic Performance Improvement of $ \hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}/\hbox{InAs}/\hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$ Composite-Channel HEMT Using Gate-Sinking Technology

Eighty-nanometer-gate In
_0.7
Ga
_0.3
As/InAs/In
_0.7
Ga
_0.3
As composite-channel high-electron mobility transistors (HEMTs), which are fabricated using platinum buried gate as the Schottky contact metal, were evaluated for RF and logic application. After gate sinking at 250degC for 3 min, the device exhibited a high g
_m
value of 1590 mS/mm at V
_d
= 0.5 V, the current-gain cutoff frequency f
_T
was increased from 390 to 494 GHz, and the gate-delay time was decreased from 0.83 to 0.78 ps at supply voltage of 0.6 V. This is the highest f
_T
achieved for 80-nm-gate-length HEMT devices. These superior performances are attributed to the reduction of distance between gate and channel and the reduction of parasitic gate capacitances during the gate-sinking process. Moreover, such superior performances were achieved through a very simple and straightforward fabrication process with optimal epistructure of the device.