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Interface of directly bonded GaAs and InP

The structure and composition of the interface of directly bonded GaAs and InP (001) wafers has been studied with various techniques in electron microscopy. For each interface three different dislocation networks have been identified and analyzed. They have been confirmed to accommodate the lattice mismatch, the tilt misfit between the two wafers, and the thermal misfit, respectively. Interdiffusion of both group-III and group-V elements takes place. Indium diffusion is enhanced by the Zn dopant and its segregation. The “cavities” at the interface, reported in the literature, have been found to be associated with indium depletion. In the case of inadequate surface preparation prior to bonding an amorphous layer of native oxide(s) forms at the interface. The actual bonding temperature Tb at which the atomic bonds construct locally across the two surfaces of the wafers is lower than the annealing temperature employed in the present experiments. It is therefore suggested that a better interface may be achieved by improving the preparation of the surfaces of the wafers with appropriate chemicals and by bonding the wafers at a lower temperature.

Interface structure ; Indium ; Doping ; Electron microscopy ; Oxide surfaces

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