Electrical transport properties in (111) growth-axis GaAlAs/GaInAs heterostructures

The effect of an internal piezoelectric field on electrical transport pheno mena has been studied in GaAlAs/GaInAs heterostructures grown on (001) and (111)B GaAs substrates. The two-dimensional electron gas (2DEG) in the stru cture was obtained by conventional modulation delta -doping in the barrier layer. The: conductivity and Nail effect were studied at room temperature a s a function of hydrostatic pressures up to 1000 MPa. The observed pressure changes of the 2DEG concentration have been compared with theoretical pred ictions, taking into account the strain-induced electric fields in the barr ier layer. The piezoresistive behaviour under uniaxial stress has also been determined. It was found that piezo-effects are more pronounced in the cas e of the material with the built-in piezoelectric field.