Chemical bonding at room temperature via surface activation to fabricate low-resistance GaAs/Si heterointerfaces

Bonding mechanism at room temperature (RT) in GaAs/Si heterointerfaces fabricated by surface-activated bonding (SAB) is examined using cross-sectional scanning transmission electron microscopy combined with low-temperature focused ion beam and time-of-flight secondary ion mass spectrometry. In the bonding process at RT, atomic intermixing at the interfaces, presumably due to the transient enhanced diffusion assisted by the point defects introduced in the surface activation process, is confirmed. The defect-assisted atomic diffusion at the interfaces, as well as the formation of atomically clean and activated surfaces, would be the key concept of SAB, by which we can create tough heterointerfaces at RT. Meanwhile, the defects on the activated surfaces would degrade the interface resistance. The degraded properties can be recovered by an appropriate annealing after the SAB processes, although the atomistic structure around the heterointerfaces would be modified during the annealing. By controlling SAB and subsequent annealing conditions, we can obtain low-resistance heterointerfaces via the optimization of the trade-off relationship between the chemical bonding strength and the electronic properties, determined by the activated surfaces before bonding.