Field dependence of mobility in Al0.2Ga0.8As/GaAs heterojunctions at very low fields

Multiple-period (Al, Ga)As/GaAs modulation doped heterojunction structures have been grown with molecular beam epitaxy. Electron mobilities of about 200 000 cm2/Vs at 10 K and 90000 cm2/Vs at 77 K with associated sheet carrier concentrations of about 2×1012 cm¿2 have been observed. The current parallel to the interfaces for low electric fields was examined as a function of lattice temperature. The electron mobility has been observed to be strongly dependent on the strength of the electric field, and hot electron effects were observable at a field as low as 10 V/cm. To our knowledge this is the first report of hot electron phenomena in GaAs at such small fields.