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

Abstract

Single period modulation doped Alx Ga1−x As/GaAs heterostructures have been grown by MBE and characterized. The incorporation of a thin undoped Alx Ga1−x As layer between the doped Alx Ga1−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 Alx Ga1−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 Alx Ga1−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.