Enlarged broad band photodetection using Indium doped TiO2 alloy thin film

An instantaneous source of Indium (In) was used to dope the TiO2 thin film (TF) on the Si substrate. The X-ray diffraction depicted the presence of rutile phases of TiO2, which shifted to the lower value 61.7 from 61.9 (2θ). Secondary ion mass spectrometry (SIMS) reveals that the diffusion of Indium ion yield decreases sharply from the surface, as approached toward the TiO2 TF-Si substrate interface. The bulk diffusion of In into TiO2 was observed at a depth of 125-200 nm, up to the edge of TiO2 TF. An inhomogeneous layer of InxTiyO2 alloy was formed during annealing process. An average of two fold enhanced photo absorption was recorded for the In doped TiO2 TF in the 300-350 nm and 450-800 nm regions respectively. The main band gap of In doped TiO2 was increased to 3.4 eV, whereas the large absorption edge was observed at 3.1 eV. The leakage current (34 nA at −0.5 V) of In doped TiO2 TF detector was significantly reduced. A maximum 2.5 times (−3.5 V) enlarged photodetection has been observed for In doped TiO2 TF device under white light illumination. The In doped TiO2 TF detector shows the broad band photodetection, with an infinitesimal delay in its photo response time as compared to undoped TiO2 TF.