Results of a transmission electron microscopy (TEM) study of directly bonded GaAs/GaN structures obtained by wafer fusion are presented. A large fraction of the interface area was found to be well bonded, with the presence of a thin (1–2 nm) amorphous layer of a native oxide at the bonded interface. The dominant defects found in nonbonded areas were cavities elongated along the GaAs
direction. Plan-view TEM study of well-bonded regions showed the presence of two dislocation networks. The first, formed at the interface to accommodate an unintentional tilt between the fused crystals, consists of a one-dimensional array of wavy dislocations located at interface steps. The second dislocation network, formed to relieve additional strain from the thermal processing of the samples, consists of a two-dimensional, irregularly spaced grid of dislocations formed on the GaAs side that runs parallel to either the GaAs
directions. © 2002 American Institute of Physics.