Transport of electrons in two-dimensional square and rectangular lateral surface superlattices

We have studied commensurability oscillations (COs) in the magnetoresistanc e of two-dimensional lateral surface superlattices (LSSLs) with patterns ha ving both square and rectangular symmetry. Square lattices of period 100 ra n fabricated on orthodox GaAs/AlGaAs heterostructures showed weak COs corre sponding to the lattice period. 100 by 170 run rectangular lattices with th e 170 nm period along the current flow direction showed significant oscilla tions corresponding to this period for transport in all directions on the w afer. When a wafer containing a thin strained layer of InGaAs close to the surface was patterned to produce square 100 run period superlattices with l arge asymmetry in the potential landscape, transport in the [01(1) over bar ] direction (on a (100) wafer) showed pronounced oscillations with a period of 100 nm period, as in one-dimensional LSSLs, while that along [011] show ed no COs at all. For transport in the [010] and [001] directions, one of t he diagonal Fourier potential components is dominant, and the commensurabil ity oscillations in both samples were identical and had an effective period of 100/root2 nm. All these results can be satisfactorily explained using a new theory of two-dimensional guiding center drift.