FRACTURE PROPERTIES OF GaAs–AlAs SUPERLATTICES STUDIED BY ATOMIC FORCE MICROSCOPY AND SCANNING ELECTRON MICROSCOPY

Abstract—GaAs–AlAs superlattices with periodicities of up to 200 nm were cleaved to expose (110) faces. These surfaces were studied using high resolution scanning electron microscopy where the secondary elec-tron images reveal contrast between the GaAs and AlAs layers and also indicate that the AlAs layers are topographically raised with respect to the GaAs. Atomic force microscopy of the same samples shows that the AlAs ridges can extend as far as 55 nm beyond the GaAs surface. Further secondary electron images of cross-sections of plastically deformed GaAs–AlAs superlattices reveal that the AlAs layers can undergo severe deformation whereas the GaAs layers fracture more readily. It is proposed that the AlAs protrusions on the (110) cleavage surface are due to the fracture behaviour of the superlattice as well as oxidation eects. # 1998 Acta Metallurgica Inc. 1