UNIFORM MULTIATOMIC STEP ARRAYS FORMED BY ATOMIC-HYDROGEN ASSISTED MOLECULAR-BEAM EPITAXY ON GAAS(331) SUBSTRATES

Coherently aligned multi-atomic step arrays are naturally formed durin g molecular beam epitaxy (MBE) of GaAs/(AlGa)As heterostructures on Ga As (331) substrates. The step height systematically increases with the substrate temperature while the lateral periodicity remains almost un changed. 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 highe r uniformity in atomic hydrogen assisted MBE allows the formation of s tep arrays, 12-13 nm high with a lateral periodicity around 250 nm, an d straight step edges over 10 mu m length. The step arrays reveal a st rong influence on the electron transport of Si-modulation-doped GaAs/( AlGa)As heterostructures with the conductivity parallel to thr: step e dges at cryogenic temperatures more than one order of magnitude larger than that perpendicular to the steps. (C) 1998 American Institute of Physics.