Lattice Imaging Analysis of GaAs/AlAs Superlattice Interface by [100] Illumination

Abstract

The superiority of the [100] illumination to the [110] illumination in lattice imaging of the GaAs/AlAs heterointerface was shown experimentally and theoretically. At the [110] illumination both the GaAs and the AlAs appeared in the same lattice image pattern and the brightness difference between the two phases was so small that the interface could not be recognized clearly. At the [100] illumination, on the other hand, adjacent crystals were distinguished from each other by not the brightness level but by the different pattern of lattice images and hence the interface was specified by the transition from one image pattern to the other. The number of atomic layers counted by the present criteria coincided perfectly with the designed number. An atomic layer step and a terrace on the interface was successfully detected by the method.