Highly photosensitive MIS structure with embedded silicon film for solar cell and photodetection applications

In this work, we report for the first time an original method to produce silicon film buried in SiO2 insulating layer for high-performance metal-insulator-semiconductor (MIS) photodetector and solar cell applications. The Si film embedded in SiO2 has been produced by partial thermal oxidation of an ultimate silicon-on-insulator (SOI) substrate. This process makes it possible to control with high precision the thickness of the silicon film and therefore the control of its electrical and opto-electric properties. The structural characterization of this new structure by high-resolution transmission electron microscopy (HR-TEM) and ellipsometric spectroscopy shows that the silicon film is monocrystalline without crystalline defects and has a homogeneous thickness. Current-voltage (I-V) and photocurrent (PC) measurements performed on the structure show that insertion of a silicon film in the insulating layer (SiO2) of an MIS structure as an active layer improves the electrical transport, increases the photocurrent by more than 100 times, and extends the spectral response of the MIS structure to the ultraviolet. These results show that the insertion of crystalline silicon film in an insulator layer of MIS structure is electrically more efficient than the insertion of Si quantum dots and could be a promising way to improve the performance of low-cost MIS-type photodetectors and solar cells that are fully compatible with CMOS technology.