Abstract
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 Ωcm2. 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 Ωcm2 were achieved after the optimization.