Zno: Regulation Of Al Thin Film Optical Band Gap Study

ZnO is a II-VI wide bandgap semiconductor which is used for various applications such as gas sensors, bulk-acoustic-wave devices, surface-acoustic-wave devices, varistors, light emitting, light detecting devices and so on. Undoped and Al doped ZnO thin films have also been widely used in transparent conducting layers because of their higher thermal stability and good resistance against hydrogen plasma processing damage compared with ITO (Sn-doped In2O3) films. Al-doped ZnO thin films are emerging as an alternative potential candidate for ITO flims recently. Al doped ZnO thin films also can obtain a tunable band gap. Especially, ZnO:Al thin films with high c-axis orientated crystalline structure along (002) plane are potential device applications in broadband Ultra-violet. photodetectors with high tunable wavelength resolution.In this paper, transparent conducting ZnO thin films doped with Al have been prepared by sol–gel method, which were characterized by X-ray diffraction, atomic force microscopy and ultra-violet spectrometer. It is found that all the thin films have a preferential c-axis orientation. With increase of Al doping, the peak position of the (002) plane is shifted to the low 2θvalue. A minimum resistivity of 6.2×10-4 ?·cm is obtained for the film doped with 1.5 mol% Al. However, the resistivity increases with increase in Al concentration. The bandgap is found to broaden with increasing dopant concentration, and it is found that doping with Al has the effect of shifting the optical absorption to the shorter wavelength, with both cases being attributed to the Burstein-Moss shift.We report a study on the fabrication and characterization of ultraviolet photodetectors based on ZnO:Al films. Using sol-gel technique, highly c-axis oriented ZnO films with 5 mol.% Al doping were deposited on Si (111) substrates. The photoconductive UV detectors based on ZnO:Al thin films, having a metal-semiconductor-metal (MSM) structure with interdigital (IDT) configuration, were fabricated by using Au as a contact metal. The characteristics of dark and photocurrent of the UV detector and the UV photoresponse of the detector were investigated. The...