Plasma-activated GaAs/Si wafer bonding with high mechanical strength and electrical conductivity

Abstract

Bonded GaAs/Si heterojunctions with high mechanical strength and electrical conductivity are important for low-cost photovoltaics and silicon-based photonics. In this work, we successfully achieved wafer-based (2 in.) GaAs/Si direct bonding structures with high strength by using the plasma-activated bonding (PAB) method. The bonding strength can be close to that of the GaAs/Si samples bonded by the surface-activated bonding method. It is found that the surface roughness and height of GaAs wafers have a greater influence on the bonding strength than Si wafers. More importantly, an ohmic n-GaAs/n-Si interface even with a low doping concentration of wafers was realized. Investigations reveal that the Ar plasma-induced damage in GaAs could be controlled at a significantly low level by using the PAB method. An thin amorphous layer existed between GaAs/Si interface, and no obvious cracks or voids were observed. Our results may provide a promising way to fabricate GaAs/Si heterojunctions for optoelectronic devices.