Dependence of electron mobility in modulation-doped GaAs-(AlGa)As heterojunction interfaces on electron density and Al concentration

The electron mobility of single modulation-doped GaAs-(AlGa)As heterojunctions is strongly dependent on electron density and Al concentration. A low-temperature persistent photoconductive effect is employed to vary the areal electron density continuously within a single sample by nearly a factor of 3. Over this density range the mobility increases monotonically by as much as a factor of 4, quasilinear with density. At equivalent carrier concentrations heterojunctions with lower Al concentration show higher mobilities. At low temperatures a peak mobility of 365 000 cm2/Vs is found at an areal density of 7.0×1011 cm−2 with an interparticle spacing equivalent to a three-dimensional density of 5.9×1017 cm−3.