Stackable InGaAs-on-Insulator HEMTs for Monolithic 3-D Integration

In this article, we have demonstrated 125-nm-gate InGaAs-on-insulator (InGaAs-OI) high-electron-mobility transistors (HEMTs) on Si substrates via wafer bonding. The highlights of this device were the i-In
_0.53
Ga
_0.47
As/i-InAs/i-In
_0.53
Ga
_0.47
As quantum-well channel for high RF performance by improving electron transport properties and the low processing temperature of 250 °C or less for monolithic 3-D integration. As a result, we obtained a current gain cutoff frequency ( f
_T
) of 227 GHz and a maximum oscillation frequency ( f
_MAX
) of 187 GHz. These results are the highest ever reported in monolithic 3-D RF transistors above L
_G
= 100 nm. In addition, through the small-signal modeling, we have found that the impact of the back-gate (BG) on RF performances of top devices is a critical issue in M3D RF systems.