Experimental and theoretical characteristics of high performance pseudomorphic double heterojunction InAlAs/In/sub 0.7/Ga/sub 0.3/As/InAlAs HEMT's

Pseudomorphic double heterojunction (DH) InAlAs/In/sub 0.7/Ga/sub 0.3/As/InAlAs HEMT's with very high cut-off frequencies and current densities have been demonstrated. DC and microwave characteristics of the double heterojunction and single heterojunction (SB) HEMT's have been compared. Two identical layers except for the dopings have been grown and fabricated using a conventional non-self-aligned process for this purpose. In order to further enhance the performance level of DH-HEMT's, a sub-0.1 /spl mu/m offset /spl Gamma/-gate self-aligned process has been used on DH layers. A minimum frequency of oscillation (f/sub max/) of 350 GHz and a current gain cut-off frequency (f/sub T/) of 180 GHz have been achieved in this way along with the full channel current of 1.2 A/mm. Theoretical simulation using 2-D ensemble Monte Carlo simulation has also been performed to optimize the DH layer structure and to study the transport characteristics of DB-HEMT's compared with SH counterparts.>