Reduction of remote impurity scattering in heavily modulation-doped GaAs and (GaIn)As quantum wells with AlAs/GaAs type-II-superlattice barriers

We present a new semiconductor heterostructure to reduce impurity scattering in remotely doped GaAs and (GaIn)As single quantum wells. By using heavy-mass X-electrons in the short-period AlAs/GaAs superlattice barriers, the potential fluctuations of the ionized Si dopants are smoothed. In 10 nm GaAs and (InGa)As single quantum wells, respective densities of about 2 x 10(16)m(-2) and 3 x 10(16)m(-2) can be achieved with a low level of remote impurity scattering. For (InGa)As single quantum wells, the reduction of the impurity scattering manifests itself as an increase of the single particle relaxation time. Structure design and growth parameters for achieving ultrahigh conductivities are discussed.