Investigation of the properties of semiconductor wafer bonding in multijunction solar cells via metal-nanoparticle arrays.

Semiconductor wafer bonding has gained attention for its use in the design of efficient optoelectronic devices. Here, we report the observation of the properties of semiconductor wafer bonding via metal nanoparticle arrays based on the current-voltage and reflectance measurements of multijunction solar cells. Based on our observation of temporal changes in current-voltage characteristics and reflectance, we have revealed that reduced contact resistance at the bonded interface involves two processes: van der Waals bonding, which occurs within a few minutes, and diffusion bonding of metal nanoparticles, which occurs in a time scale of days. The mechanism of wafer bonding via metal nanoparticles is discussed based on its dynamical aspects, including the roles of liquid capillarity and alloy formation at the interface. [ABSTRACT FROM AUTHOR]