Fabrication and characterization of InAlAs/InGaAs striped-channel modulation-doped field effect transistors

Abstract

Striped-channel modulation-doped field effect transistors (MODFETs), in which the transport of electrons from source to drain is restricted to multiple parallel channels, have been fabricated on a lattice-matched InAlAs/InGaAs heterostructure and characterized at dc and rf frequencies. dc performance of the striped-channel devices shows increased transconductance when normalized with the actual width of the striped channels. This may be attributed to improved control of electron concentrations in the channels since the depletion layer induced by the controlling gate is not only from above, but from below and in lateral directions as well, resulting in improved electron confinement. A reduction of output conductance of the striped-channel device is observed when compared to a conventional MODFET. This is interpreted to be a result of an enhanced barrier between the buffer and channel layers of the striped-channel device, which reduces the injection of hot electrons into the buffer. rf characteristics of the devices show a reduction of cutoff frequency for devices having smaller channels. dc measurements at cryogenic temperatures were performed to investigate the possibility of mobility enhancement in the striped-channel devices.