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-oninsulator
(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.