Investigation of Wafer-Bonded InAs/Si Heterojunction by Transmission Electron Microscopy
An InAs/Si heterojunction formed by a wet wafer bonding method with an annealing temperature of 350 °C was investigated by transmission electron microscopy (TEM). InAs and Si were observed to be uniformly bonded without any voids in a 2-µm-long field of view in a bright-field TEM image. A high-resolution TEM image revealed that, between the InAs and Si lattice images, there existed a transition layer having an amorphous-like structure 10–12 nm thick, which had the role of atomically combining the two crystals. The transition layer was separated into two layers of different brightnesses in a high-angle annular dark-field scanning TEM image. The distributions of In, As, Si, and O atoms in the vicinity of the heterointerface were examined by energy dispersive X-ray spectroscopy. The amounts of In, As, and Si atoms gradually changed within a 20-nm-thick intermediate layer including the transition layer. Accumulated O atoms were detected in the transition layer.