InAlAs/InGaAs channel composition modulated transistors with InAs channel and AlAs/InAs superlattice barrier layer

We have successfully fabricated a new type of InAlAs/InGaAs heterojunction FET (HJFET) with modulated indium composition channels, called channel composition modulated transistors (CCMTs) in which an InAs channel is sandwiched by In/sub 0.53/Ga/sub 0.47/As/In/sub 0.8/Ga/sub 0.2/As sub-channels. The fabricated devices also employ an AlAs/InAs superlattice as a barrier layer against impurity contamination to provide high thermal stability. A 0.2-μm T-shaped gate device exhibits a g/sub m/ of 1370 mS/mm, F_T of 180 GHz and F_max of 210 GHz at a low drain bias of 1.0 V. In high-temperature DC life tests conducted at more than 230/spl deg/C, the devices exhibited less than a 3% degradation in I/sub dss/ and g/sub m/ after 1000 h. This demonstrates that these newly-developed CCMTs incorporating AlAs/InAs superlattice insertion technology can offer high-performance and highly-reliable InP-based HJFET´s for various microwave and millimeter-wave applications.