Investigation of the spatial variation of scattering centers in parabolic quantum wells

The wave functions inside a parabolic quantum well have been tuned in growt h direction by suitable gate voltages, and the elastic scattering times hav e been extracted from low-temperature transport measurements. We have inves tigated the case of two occupied subbands using a semiclassical model for t he magnetotransport, and find in the case of constant electron density, tha t the scattering times depend on the position of the wave function with res pect to the as-grown parabola. While the Drude scattering times of the lowe st two subbands are essentially symmetric with respect to the position of t he electron distribution being centered in the as-grown parabola, the quant um scattering time tends to increase when the electron gas is shifted towar ds the sample surface. We show that wave function tuning under constant ele ctron density gives additional information on the elastic scattering in qua ntum wells, in complement to the standard method of investigating the densi ty dependence of the scattering times. (C) 1998 Elsevier Science B.V. All r ights reserved.