Room-temperature bonding of GaN to Al using Ar-Beam surface activation

As-grown n-type GaN has been bonded successfully to polycrystalline Al by surface activated bonding in an ultrahigh vacuum at room temperature. The microstructure, bonding strength, and electrical characteristics of the bonded GaN/Al interface have been investigated using transmission electron microscopy (TEM), tensile strength testing, and current-voltage (I-V) measurements. For producing active surfaces,argon-fast atom beam sputteringsource (acceleration voltage: 1.5 kV, current: 15 mA) was used. The TEM study showed thata nearly continuous amorphous thin interlayer composed of mainly Al with a thickness ofabout 10 nm was observed at the bonded interface. The tensile strength of GaN/Al samples was in the range of 14-19 MPa. The results of I-Vmeasurements showed that the n- GaN/Al interface without thermal annealing was rectifying and became ohmic after thermal annealing in N₂gas ambient at 600°C.