Investigation of metal-oxide semiconductor field-effect transistor-like Si/SiO2/(nano)crystalline PbS heterostructures

The influence of the gate voltage on photoconductivity in p–Si/SiO2/(nano)crystalline PbS, Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET)-like structures is investigated. The effect on the photo-signal in the wavelength range 500–1180 nm is opposite compared to the effect in the wavelength range 1600–2500 nm: a negative gate voltage increases the signal in the short wavelength range and decreases it for the long wavelength range. The opposite is valid for a positive gate bias. An on-off ratio better than 85 times is obtained for the spectral range 500–1180 nm, corresponding to the absorption in p–Si and better than 3.5 times for the spectral range 1600–2500 nm corresponding to the absorption in the (nano)crystalline PbS region, respectively.