Experimental and theoretical electron mobility of modulation doped AlxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy

Abstract

Single period modulation doped Al_x Ga_1−x As/GaAs heterostructures have been grown by MBE and characterized. The incorporation of a thin undoped Al_x Ga_1−x As layer between the doped Al_x Ga_1−x As and undoped GaAs layers further improves the electron mobility through the reduction of remote donor scattering. Electron mobilities as high as 8165, 80 900, and 115 000 cm² V⁻¹ s⁻¹ at 300, 78, and 10 K respectively, for an average sheet electron concentration of 5×10¹¹ cm⁻² were obtained. The best mobility was obtained when the undoped Al_x Ga_1−x As layer thickness was 75 Å for both x = 0.25 and x = 0.33. These figures represent the best mobilities associated with single period Al_x Ga_1−x As/GaAs structures reported to date. Good agreement between the experiments and mobility calculations have also been obtained. The theory is based on heavily screened remote impurity scattering and quasi‐two‐dimensional electron‐phonon interaction.