Yeni Nesil İnce Filmler İle Optoelektronik Uygulamaların Araştırılması

Abstract

The aim of this study is to develop easy to fabricate and inexpensive ultraviolet photodetectors with metal oxide thinfilms and to improve or change the performance of those devices using designed nanostructures. For this purpose Titanium Dioxide (TiO2) and Zinc Oxide (ZnO) materials were selected which are used for ultraviolet photodetector fabrication. As the deposition method for those materials one of the physical deposition methods, RF Magnetron Sputtering was selected, which is easy to utilize and rather inexpensive in terms of operation. During the early stages of the study, TiO2 thin film deposition and device fabrication optimization studies were performed. The properties of the annealed and Oxygen plasma treated thin films were investigated, the performances of the photodetectors fabricated using treated and untreated thin films were compared and found out that the photodetectors fabricated using untreated thinfilms were performing comparably with the photodetectors fabricated with treated thinfilms. The photodetectors fabricated with untreated thin films showed breakdown voltages larger than 50 V, dark curent density less than 2.1x10-8 A/cm2, 1.8 A/W responsivity, %1750 internal quantum efficiency and 9 s and 3.5 s rise and fall times respectively. Although these results are similar with the results ontained from treated thin films given in the literature, they are interesting because the photodetectors were fabricated by simple and cheap processes without any post annealing or plasma treatment. The next stage of the study was to design nanoplasmonic structures on those well performing photodetectors to improve or modify the spectral response of the photodetector for specific applications. Integrating the designed nanoplasmonic structure with the photodetetor the response of the photodetector in UVB bant was reduced by 60%. This was a demonstration of the usage of nanoplasmonic structures (which are mostly used in IR bant) for the modification of spectral response of the photodetectors for specific applications and the first usage of nanoplasmonic filters in UV bant. During the following stages of the study, photodetectors were fabricated using as deposited ZnO thin films with breakdown voltage of larger than 100 V, dark current densities as low as 100 pA/cm2 at 100 V bias voltage, respective rise and fall times of as low as 22 ps and 8 ns and responsivity of 0.35 A/W were obtained. Another phase of the ZnO thin film photodetector study was investigating the optoelectronic properties of Ge nanoparticle doped ZnO thin films and developing devices using this material. The characterization of the deposited thin films were done and photoconductor, Si heterojunction and TiO2 heterojunction devices as the first concept in literature were fabricated and characterized.