Interface states in modulation-doped In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As heterostructures

Systematic admittance measurements have been performed on the heterojunction capacitor in In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As modulation-doped heterostructures and on bulk Si-doped In/sub 0.52/Al/sub 0.48/As Schottky diodes grown by molecular-beam epitaxy. From the frequency-dependent capacitance and conductance characteristics, the density of any traps at and/or near the interface and their corresponding time constants were calculated to be in the range of 10/sup 12/-10/sup 13/ cm/sup -2/ and 10/sup -7/-10/sup -6/ s, respectively. Compared to AlGaAs/GaAs heterostructures, the In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As system was found to have a higher density of interface states. These results suggest that the interface quality of the In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As heterostructure is not as perfect as that in AlGaAs/GaAs. This may be largely due to a poorer interface resulting from lattice mismatch and growth front surface roughness, and alloy clustering causing a higher density of localized states in In/sub 0.52/Al/sub 0.48/As.<
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