Room-Temperature Bonding of GaN to Al Using Ar-Beam Surface Activation

Abstract

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 sputtering source (acceleration voltage: 1.5 kV, current: 15 mA) was used. The TEM study showed that a nearly continuous amorphous thin interlayer composed of mainly Al with a thickness of about 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-V measurements showed that the n- GaN/Al interface without thermal annealing was rectifying, and became ohmic after thermal annealing in N₂ gas ambient at 600°C.