CORRELATIONS OF THE REMOTE IMPURITY CHARGES - A METHOD OF 2DEG MOBILITY TUNING IN GAAS ALGAAS HETEROSTRUCTURES/

Low temperature 2DEG mobillity and carrier concentration measurements made on two modulation doped GaAs/AlGaAs heterostructures are describe d. We demonstrate that, depending on the method which is used to popul ate the metastable donor states of Si-remote impurity, different value s of electron mobility can be obtained for the same 2DEG density and i n the same heterostructure. Concept of the correlation in the spatial distribution of the impurity charges (i.e. positively and negatively c harged states of Si donor), caused by the Coulomb interactions is empl oyed to explain our experimental finding. The invoked effect induces a strong reduction of the 2DEG scattering and can produce the mobility enhancement by as much as a factor of two over its value with a random distribution of impurity charges.