ELECTRON-MOBILITY IN SELECTIVELY SI-DOPED GAAS N-AL0.3GA0.7AS QUANTUM-WELL HETEROSTRUCTURES WITH SUPER-FLAT INTERFACES GROWN ON (411)A GAASSUBSTRATES BY MOLECULAR-BEAM EPITAXY/

Reduced roughness of GaAs/Al0.3Ga0.7As heterointerfaces formed on (411 )A substrates by Molecular Beam Epitaxy (MBE) was confirmed by measuri ng Two Dimensional Electron Gas (2DEG) mobility in selectively Si dope d GaAs/N-Al0.3Ga0.7As Quantum Well (QW) structures with 4, 6, 8, or 50 -nm thick GaAs wells. Below a QW thickness (L-w) of 8 nm, the 2DEG mob ility at 15 K was mainly determined by interface roughness scattering and rapidly decreases with decreasing well thickness. The 2DEG in the (411)A selectively doped QW sample with L-w=4 nm has 34% higher mobili ty (mu = 32 500 cm(2)/VS) at 15 K than that of the (100) sample simult aneously grown (24 200 cm(2)/Vs). Every (411)A sample with L-w less th an or equal to 8 nm has 24-34% higher 2DEG mobility than the (100) sam ple simultaneously grown. This result indicates that smoother GaAs/Al0 .3Ga0.7As interfaces were realized on the (411)A substrates. The (411) A sample with the 50-nm thick well shows 84% higher 2DEG mobility than the (100) sample simultaneously grown and its mobility is not determi ned by interface roughness scattering but ionized impurity scattering, which may suggest that MBE growth of GaAs and AlGaAs on the (411) GaA s substrates reduces unintentional impurity incorporation. (C) 1998 El sevier Science B.V. All rights reserved.