Optimization Of Alas/Algaas Quantum Well Heterostructures On On-Axis And Misoriented Gaas (111)B

We report systematic growth optimization of high Al-content AlGaAs, AlAs, and associated modulation-doped quantum well (QW) heterostructures on on-axis and misoriented GaAs (111)B by molecular beam epitaxy. Growth temperatures T-G > 690 degrees C and low As-4 fluxes close to group III-rich growth significantly suppress twin defects in high-Al content AlGaAs on on-axis GaAs (111)B, as quantified by atomic force and transmission electron microscopy as well as x-ray diffraction. Mirror-smooth and defect-free AlAs with pronounced step-flow morphology was further achieved by growth on 2 degrees misoriented GaAs (111) B toward [0 (1) over bar1] and [2 (1) over bar(1) over bar] orientations. Successful fabrication of modulation-doped AlAs QW structures on these misoriented substrates yielded record electron mobilities (at 1.15 K) in excess of 13 000 cm(2)/Vs at sheet carrier densities of 5 x 10(11) cm(-2). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4711783]