Improved photoresponse characteristics in Se-doped Si photodiodes fabricated using picosecond pulsed laser mixing

Silicon doped with selenium beyond the solid solubility limit was prepared by picosecond pulsed laser mixing of an evaporation-deposited Se film with the underlying p-Si wafer. Photodiodes fabricated from this material exhibit enhanced spectral response over the range from 400 to 1600 nm. The responsivity strongly depends on reverse bias voltage and pulsed laser fluence. At 5 V bias, a room-temperature responsivity of 16 A W−1 at 1000 nm is obtained. At below-bandgap wavelengths, measurable responsivities of 15 mA W−1 at 1330 nm and 12 mA W−1 at 1550 nm are also observed. Extended Se impurity states might form within Si bandgap and contribute to the prominent photoresponse in these photodiodes.