PERIODIC MESOSCOPIC STEP ARRAYS BY STEP BUNCHING ON HIGH-INDEX GAAS-SURFACES

The direct formation of mesoscopic surface corrugations on high-index GaAs substrates during growth by molecular-beam epitaxy is reported. T he accumulation of microscopic steps on GaAs (210) to produce one-dime nsional step arrays with a 230 angstrom lateral periodicity is followe d by reflection high-energy electron diffraction. The surprisingly hig h uniformity of the resulting mesoscopic step array is directly confir med by atomic force microscopy. The shape of the steps is imaged by hi gh-resolution transmission electron microscopy. Being comparable to th e exciton Bohr radius in GaAs this length scale of the lateral periodi city is of particular importance for modulating the electronic propert ies of GaAs-based heterostructures. Pronounced red shifts in the lumin escence of undoped GaAs/AlAs multilayer structures and an enhanced int ensity at room temperature are observed. n-type modulation-doped heter ostructures exhibit an anisotropic conductivity.