LATTICE-MISMATCHED IN0.53GA0.47AS/IN0.52AL0.48AS MODULATION-DOPED FIELD-EFFECT TRANSISTORS ON GAAS - MOLECULAR-BEAM EPITAXIAL-GROWTH AND DEVICE PERFORMANCE

We describe here the properties of In0.53Ga0.47As/ In0.52Al0.48As modulation-doped heterostructures and field-effect transistors grown directly by molecular-beam epitaxy on GaAs substrates. The generation and nature of dislocations in the films have been studied by transmission-electron microscopy. The final heterostructure contains a series of compositional steps of InxGa1-xAs (0≤x≤0.53) to generate and control the dislocation movement. The modulation-doped heterostructures are characterized by μ300 K=8 150 cm2/V s (ns=2.7×1012 cm-2) and μ20 K=26 100 cm2/V s (ns=2.1×1012 cm-2) which compare very favorably with values measured in similar lattice-matched heterostructures on InP. 1.4-μm gate-modulation-doped field-effect transistors exhibit gm(ext)=240 mS/mm and fT=21 GHz. The drain current variation with gate bias is linear and the transconductance is uniform over a sizeable voltage range. These material and device characteristics indicate that InxGa1-xAs/InxAl1-xAs transistors (with x varying over a certain range to vary ΔEc) can be designed on GaAs or even other mismatched substrates.