Fast atom beam activated wafer bonds between n-Si and n-GaAs with low resistance

Fast atom beam activated direct wafer bonds can be used to combine GaAs and Si semiconductor structures and to achieve high bond strength and optical transparency. Some applications require a low ohmic resistance between the materials. Therefore, IV-characteristics of n-type wafer bonds between n-Si and n-GaAs were thoroughly investigated. n-Si/n-Si bonds showed ohmic resistance below 2.5 × 10−3 Ocm2. However diode like IV-curves were found for both n-GaAs/n-GaAs and n-Si/n-GaAs bonds. This can be explained by the formation of a potential barrier at the interface, caused by carrier trapping in fast atom beam induced defects. Hall measurements of n-GaAs after fast atom beam treatment confirmed both, a reduction of the active carrier concentration, and the electron mobility. It was found that thermal annealing and higher bond temperatures can help reducing the potential barrier height at the n-Si/n-GaAs interface and thus lower the electrical bond resistance by healing crystalline defects. Highly conductive n-Si/n-GaAs wafer bonds with an interface resistance below 3.6 × 10−3 Ocm2 were achieved after the optimization.