Beschreibung:
<jats:p>Coherently aligned multi-atomic step arrays are naturally formed during molecular beam epitaxy (MBE) of GaAs/(AlGa)As heterostructures on GaAs (331) substrates. The step height systematically increases with the substrate temperature while the lateral periodicity remains almost unchanged. With atomic hydrogen irradiation the step height is larger by more than a factor of 2 compared to that in conventional MBE which is attributed to a larger surface migration length of adatoms. The higher uniformity in atomic hydrogen assisted MBE allows the formation of step arrays, 12–13 nm high with a lateral periodicity around 250 nm, and straight step edges over 10 μm length. The step arrays reveal a strong influence on the electron transport of Si-modulation-doped GaAs/(AlGa)As heterostructures with the conductivity parallel to the step edges at cryogenic temperatures more than one order of magnitude larger than that perpendicular to the steps.</jats:p>