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 ha ve 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, name ly the lager thicknesses and the doping level in the barrier layer, on the carrier concentration n(s) in the channel, Modulation-doped heter ostructures with a 100 Angstrom strained indium-rich channel have been grown by molecular beam epitaxy different indium compositions and gro wth 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 concentra tion, the mobility drops sharply, which correlates with formation of m isfit dislocations in the channel, observed on transmission electron m icroscopy micrographs of these structures, For an indium concentration of 75%, the mobility has been improved, first, by using a low V/III b eam Equivalent pressure ratio, that produces a close to stoichiometry material, second by using interface growth interruption under cation s tabilization to reduce the interface roughness. HEMT devices have been processed on these heterostructures. The static I-V characteristics o f 2 x 150 mu m(2) transistors revealed a 66% increase of the transcond uctance when the channel indium concentration is increased from 53% to 75%.