Design, fabrication and characterisation of a ZnO-based photodetector

The structural, optical and electrical properties of the n-type zinc oxide (ZnO) thin film samples with different annealing temperatures grown by pulsed filtered cathodic vacuum arc deposition have been investigated within the scope of this thesis work. Utilizing the hall measurements, a carrier concentrations, resistivity and mobility of ZnO thin film samples were obtained. The data obtained as a result of Hall Effect measurement were compared based on different annealing temperatures. By using the results of transparency measurements of ZnO thin films, the band gap energy has been calculated and further the obtained data were compared based on different annealing temperature. The information about a grain sizes of ZnO in thin films was obtained from the XRD and SEM measurements. The informations about elemental composition of samples was obtained from EDS measurements. The n-type ZnO samples analyzed within the scope of the study went through the interdigital electrode mask fabrication process where device fabrication was carried out in the metal-semiconductor-metal (Metal Semiconductor Metal, MSM) photodetector structure. The optical and electrical properties of the fabricated MSM photodetectors were also analyzed. The MSM photodetectors were studied under solar simulator lamp without filter and also under 370 nm filter, photoconductivity was analyzed under +5 V supply voltage and current-voltage (I-V) measurements were performed between range of -5 V and +5 V. As a result of aforementioned measurements the detector parameters were determined and were compared based on different annealing temperatures. The photoconductivity measurements were performed with 0.25 V intervals in supply voltage range of 0.25 V to -5 V in order to determine an ideal working supply voltage of photodetector. All samples analyzed within the scope of this thesis have been grown by PFCVAD method in the Physics Department at Çukurova University, Faculty of Science. The transparence measurements, XRD and Hall Effect measurements of ZnO thin film samples were carried out in the Physics Department of Çukurova University. Throughout this thesis work all ZnO MSM photodetectors were fabricated by employing the photolithography, one of widely used lithography methods. The fabrication process was carried out in the Advanced Lithographic Methods Laboratory, which is under constitution of the Nano and Optoelectronic Research Laboratory at Istanbul University, Faculty of Science. The optical and electrical characterization of all ZnO MSM type photodetector samples fabricated within the scope of thesis were carried out at the Nano and Optoelectronics Research Laboratory at Istanbul University, Physics Department.