THz Frequency HEMTs: Future Trends and Applications

In recent years the outstanding RF performance of InGaAs high electron mobility transistors (HEMTs) could be further improved by rigorous scaling the gate length of the devices down to 20 nm. Examples of applications in 300 GHz communication and radar systems as well as cryogenic receivers are presented. Due to the reduced gate to channel separation the HEMT has entered the quantum regime where the tunneling effect starts to dominate the device characteristics and preclude further device improvements. To overcome this quantum limit of the classical HEMT, Fraunhofer IAF has started to investigate InGaAs channel MOSHEMTs where the metal/semiconductor Schottky barrier is replaced by an oxide layer to suppress the tunneling leakage currents. This approach combines the the excellent high frequency performance of III/V semiconductors with the superior characteristics of the oxide gate barrier as used in Silicon MOSFETs.