چكيده به لاتين
Abstract:
In the recent years, many studies have been focused on high-performance UV photodetectors. The applications of this devices in military and civilian fields is well known. Because of the growing demands to make reliable and miniaturized ultraviolet detection systems, it should be to develop semiconductor-based ultraviolet photodetectors. Among different semiconductors, ZnO with direct and large band gap is a good choice to make ultraviolet photodetector. In comparison to the bulk materials, nanostructures are very sensitive to light. ZnO nanostructures are suitable for UV detection due to the wide bandwidth, low cost, strong radiation and high chemical stability. So far, many researches on ultraviolet photodetectors based on ZnO nanostructures are practical, but simulation of these structures is the smooth way for more extensive research on these detectors. The purpose of this thesis is the design and simulation of ultraviolet photodetectors based on ZnO nanostructures.
To carry out the simulation, ZnO is initially defined in FDTD and DEVICE software. Therefore, the structural characteristics are needed to be explored to design photodetector proportional to existing practical works. The reported results for construction of these devices show that the radius of the nanorods is in the range of 25 to 70 nm and their length is in the range of 0.5 to 2.5 micrometers generally.
According to the results of our thesis, we can adjust band gap of structure in the range of 3.107 eV to 3.142 eV by means of different nanorods and seed layer thicknesses. The minimum dark current was obtained about 21 fA for nanorods with 25 nm radius. In addition, for the structure proposed in this thesis in comparison with conventional structures mentioned in the context, the lowest dark current (about 16 pA) and the maximum SNR (about 78 dB) was obtained. Values of spectral response and quantum efficiency versus wavelength show that ZnO photodetector have maximum of response and optical current in 365 nm wavelength.
Keywords: Ultraviolet photodetector, ZnO nanostructures, optical properties, electrical properties
