Abstract
Ge/Si integration receives a lot of attention for both electronic and photonic devices. For example, Ge/Si-based high-mobility transistors and high-speed photodetectors have been demonstrated with superior performances. However, pure Ge grown on Si is critical due to the lattice mismatch (4%) between Si and Ge. Direct epitaxial growth of Ge on Si usually requires special process techniques and tools. In addition, Ge epitaxial growth often requires a high-temperature process condition for an extended period of time to achieve high crystal quality. Nevertheless, the resultant thermal budget could degrade the device properties and complicate the integration with ICs. Another approach for Ge/Si hetero-integration is a direct wafer or die bonding of Ge onto Si wafers. However, removing the bonded substrates could be a waste of material. Furthermore, bonding surface topography often affects the bonding yield very much. Previously, rapid melt growth (RMG) of Ge on insulator showed a promising way for the integration of high-quality Ge with ICs. However, through this process, a Ge/Si heterojunction can’t be made since the Ge layer has to be separated from the Si surface by a dielectric. In this paper, a novel process using a self-aligned microbonding technique to directly make the RMG Ge strips contacted on SOI waveguides. A microbonded Ge/Si PIN waveguide photodetector is demonstrated with good performance in dark current, operation bandwidth, and responsivity.