Scattering and electron mobility in combination-doped HFET-structures AlGaAs/InGaAs/AlGaAs with high electron density

Molecular-beam epitaxy is used for growing structures differing in doping technique and doping level and having a high two-dimensional-electron concentration $n_s$ in the quantum well. The effect of doping combining uniform and $\delta$ doping on the electron-transport properties of heterostructures is investigated. A new type of structure with a two-sided silicon $\delta$ doping of GaAs transition layers located on the quantum-well boundaries is proposed. The largest value of electron mobility $\mu_{\mathrm{H}}$ = 1520 cm$^2$/(V s) is obtained simultaneously with a high electron density $n_s$ = 1.37 $\times$ 10$^{13}$ cm$^{-2}$ at 300 K with such a doping. It is associated with decreasing electron scattering by an ionized impurity, which is confirmed by the carried out calculations.