Novel InAlAs/InGaAs heterojunction FETs with modulated indium composition channel and AlAs/InAs superlattice barrier layer

Novel InAlAs/InGaAs heterojunction FETs (HJFETs) with modulated indium composition channels, named CCMTs (Channel Composition Modulated Transistors), have been successfully fabricated, 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 channel structure is designed to improve electron transport and electron confinement by increase effective indium content in consideration of channel electron distribution. The fabricated devices also employ an AlAs/InAs superlattice as a barrier layer against impurity contamination for high thermal stability. A 0.2 /spl mu/m T-shaped gate device exhibits gm of 1370 mS/mm, and Ft of 180 GHz at a low drain bias of 1.0 V. In high temperature and DC life test conducted at more than 230/spl deg/C, the devices exhibited less than 3% degradation after 100 hrs, which shows the developed CCMTs with AlAs/InAs superlattice insertion technology can offer high-performance and highly-reliable InP-based HJFETs for various microwave and millimeter-wave applications.