Fabrication of Visible-Enhanced Nanostructured Mn 2 O 3 /Si Heterojunction Photodetector by Rapid Thermal Oxidation

Nanostructured Mn 2 O 3 films were prepared by the rapid thermal oxidation of MnS films deposited on glass and silicon substrates by means of chemical spray pyrolysis at different molar concentrations. The rapid thermal oxidation (RTO) of MnS film to prepare Mn 2 O 3 film was performed using halogen lamp at temperature of 600 °C and time of 80s. X-ray diffraction (XRD) results confirmed the formation crystalline Mn 2 O 3 film with cubic structure. Scanning electron microscope (SEM) images of Mn 2 O 3 film revealed that the morphology of the film depends on the molar concentration and the grain size decreased with increasing the molar concentration. The optical band gap of Mn 2 O 3 thin films was in the range of 2.8–3.15 eV depending on molar concentration. Raman-active modes of Mn 2 O 3 were observed at 305, 500, 648, and 700 cm −1 . The AFM investigation of the films show homogenous surface and the root mean square of surface roughness was increased as molar concentration increased. Hall effect measurements confirm that Mn 2 O 3 films were p-type. The optoelectronic properties, namely, responsivity, external quantum efficiency, and detectivity of p-Mn 2 O 3 /p-Si heterojunction photodetector as a function of molar concentration were investigated at room temperature. The current-voltage characteristics under dark and illuminated conditions were investigated and showed that the best junction characteristics was found for p-Mn 2 O 3 /n-Si prepared at 0.1 M. The maximum responsivity and detectivity were 0.5A/W and 7.2 × 10 12 Jones at 500 nm for Mn 2 O 3 /Si photodetector fabricated at 0.1 M.