Fabrication of high photosensitivity nanostructured n-Fe2O3/p-Si heterojunction photodetector by rapid thermal oxidation of chemically sprayed FeS2 film

Abstract

In this study, we have reported a novel route for the preparation of α-Fe2O3 by rapid thermal oxidation RTO of chemical sprayed FeS2 film at 550 °C/20 s condition under oxygen ambient. The direct optical band gap of Fe2O3 was 2.6 eV, while its indirect energy gap was 1.7 eV. The x-ray diffraction XRD studies show that the FeS2 film has pyrite cubic structure and changed to rhombohedral α-Fe2O3 film after oxidation. Scanning electron microscope SEM and transmission electron microscope TEM investigations confirm the formation of Fe2O3 nanorods with a diameter of 65 nm. Energy dispersive x-ray analysis EDX confirms complete conversion of the FeS2 to Fe2O3 film after RTO process. Raman shift data of Fe2O3 shows the presence of five Raman active vibration modes indexed to A1g and E1g modes. The dark and illuminated current-voltage properties of n-Fe2O3/p-Si heterojunctions have been investigated in the absence of the buffer layer and the ideality factor of n-Fe2O3/p-Si was 2.7. The responsivity of Fe2O3/Si photodetector was 0.51 A W−1 at 500 nm and 0.37 A W−1 at 850 nm. The specific detectivity of the photodetectors was measured as a function of wavelength. The rise time of the photodetector was measured and it was around 60 ns. The energy band line-up of n-Fe2O3/p-Si heterojunction was demonstrated under illumination condition.