Design and growth investigations of strained InxGa1-xAs/InAlAs/InP heterostructures for high electron mobility transistor application

Strained InxGa1-xAs/InAlAs modulation-doped heterostructures on InP have been studied theoretically and experimentally. Simulations based on self-consistently solving the Schrodinger-Poisson equations have been performed to investigate the influence of the design parameters, namely the lager thicknesses and the doping level in the barrier layer, on the carrier concentration n(s) in the channel, Modulation-doped heterostructures with a 100 Angstrom strained indium-rich channel have been grown by molecular beam epitaxy different indium compositions and growth temperatures, highest performances in term of n(s) x mu parameter, have been obtained for an indium concentration of 75% in the channel, at a growth temperature of 500 degrees C, For higher indium concentration, the mobility drops sharply, which correlates with formation of misfit dislocations in the channel, observed on transmission electron microscopy micrographs of these structures, For an indium concentration of 75%, the mobility has been improved, first, by using a low V/III beam Equivalent pressure ratio, that produces a close to stoichiometry material, second by using interface growth interruption under cation stabilization to reduce the interface roughness. HEMT devices have been processed on these heterostructures. The static I-V characteristics of 2 x 150 mu m(2) transistors revealed a 66% increase of the transconductance when the channel indium concentration is increased from 53% to 75%.