Single-crystalline silicon quantum well embedded in SiO2 thin layer for broadband photodetection and energy harvesting

In recent years, silicon nanocrystals embedded in insulator thin layers have attracted much interest for developing metal–insulator–semiconductor optoelectronic devices, but crystalline silicon quantum wells not yet developed because of the difficulty of making a crystalline quantum well-embedded in an amorphous dielectric layer. In this work, we report an original method for the fabrication of single-crystalline silicon quantum wells embedded in an SiO2 thin layer for high-performance photodetectors and solar cell applications. The fabrication method is based on thermal treatment of ultra-thin silicon-on-insulator (UT-SOI) fabricated via smart-cut. High-resolution transmission electron microscopy (HR-TEM) and spectroscopic ellipsometry structural investigations show that the silicon quantum well-embedded in the SiO2 layer is single-crystalline, free of structural defects, and has a uniform thickness perfectly suitable for optoelectronic applications. Opto-electrical studies using current–voltage spectroscopy (I–V) and photocurrent spectroscopy show that silicon quantum wells inserted into a metal–insulator–semiconductor (MIS)-based device improve electrical transport and increase very high photocurrent more efficiently than silicon nanocrystals. The results obtained show that these single-crystalline silicon quantum wells embedded in SiO2 are very promising for developing high-performance silicon photodetectors and solar cells compatible with CMOS technology.