Periodicities associated with low-order AlAs/GaAs superlattices

The use of molecular beam epitaxy to produce heterostructures has made it possible to better study superlattices with monolayer and submonolayer period spacings. In this work we examine the physical properties for the superlattice system (GaAs) n 1 (AlAs) n 2 /GaAs(001) for low values of n 1 and n 2 , i.e. n 1 = n 2 = 3,6,12. Normal, interrupted growth, and migration-enhanced epitaxy growth techniques were used to grow the superlattice structures and the X-ray diffraction spectra were obtained and the major and satellite peak positions analyzed. An analysis of the major diffraction peaks and their associated satellites exhibited superlattice periodicity in good agreement with theory. Diffraction peaks were also observed in regions adjacent to the primary diffraction peaks which did not occur in the expected satellite positions. An analysis of these peaks relative to the primary peaks indicates periodicities which are greater than the intended period. One possible cause for these periodicities is variations in growth conditions which occur while the superlattice is being grown. An understanding of low-order superlattices is important for structures which are dependent on interface sharpness.