OBSERVATION OF PIEZOELECTRIC FIELD-INDUCED CARRIERS IN ALGAAS INGAAS STRAINED-LAYER HETEROSTRUCTURES

Hall effect measurements of GaAs/AlGaAs/InGaAs strained-layer heterostructures grown on [100], [311], and [111] substrates have been performed and it is observed that the two-dimensional carrier density is a strong function of growth orientation. The observed changes in carrier density are in the range of 5 x 10(11)-1.6 x 10(12) cm-2 and are consistent with the generation of piezoelectric fields in [N11] orientated strained-layer heterostructures. These strain-induced effects can be used to alter the threshold voltages of field-effect transistor or produce large carrier densities without modulation doping.