Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Investigation of the Photo-Response of Graphene Silicon Photodetector in the Ultraviolet Region(01. Izmir Institute of Technology, 2024) Kaplan, Çiçek; Çelebi, Cem; Ünverdi, ÖzhanIn this thesis, we focus on the optoelectronic properties of p-type graphene and n-type Silicon (Gr/Si) Schottky barrier photodiode according to the number of layers in the ultraviolet region (UV). The I-V measurements were conducted at an applied bias voltage between -0.5 and 0.5 V for each Gr/Si heterojunction. The I-V measurements taken under dark conditions showed that all Gr/Si samples with 2-, 4- and 6-layers graphene electrodes exhibited rectifying Schottky junction character, but all device's reverse saturation currents (I0) were different. Schottky barrier heights (ΦB) of the samples with 2-, 4- and 6-layers graphene electrodes were determined using the I0 values obtained from I-V measurements. Compared to the ΦB value of the sample with 2 layers graphene electrode, the ΦB of the sample with 4 layers of graphene electrode increased to ~0.82 eV, and then ΦB was found to decrease to ~0.79 eV for the 6-layer graphene electrode. Additionally, photo-response measurements were carried out at zero bias voltage and in the wavelength range of 250 – 400 nm to determine the spectral response (R) of the devices in the UV region. Compared to the device with 2 layers graphene electrode, R of the sample with 4 layers graphene electrode increased by 3 times. The result obtained revealed that using 4-layer graphene as a light-transparent electrode, Gr/Si Schottky barrier photodiode is the most applicable option for sensitive detection of light in the UV region.Master Thesis The Impact of Adsorbates on the Optoelectronic Properties of Graphene/Silicon Based Schottky Barrier Photodiodes(01. Izmir Institute of Technology, 2020) Şahan, Nusret; Çelebi, CemThe aim of this study is to investigate the effect of atmospheric adsorbates on the electronic and optoelectronic properties of graphene/n-type Silicon (Gr/n-Si) based Schottky barrier photodiodes. Wavelength resolved photocurrent spectroscopy and transient photocurrent spectroscopy measurements conducted under high-vacuum conditions revealed that the adsorbates cause hole doping in graphene and hence increase the zero-bias Schottky barrier height of the Gr/n-Si heterojunction from 0.71 to 0.78 eV. Adsorbate induced increment in the barrier height promotes the separation of photo-excited charge carriers at the depletion region of the heterojunction and leads to an improvement in the maximum spectral response (e.g., from 0.39 to 0.46 A W^-1) and response speed of the Gr/n-Si photodiode in the near-infrared region. The experimentally obtained results are expected to give an insight into the adsorbate induced variations in the rectification and photo-response characters of the heterojunctions of graphene and other 2D materials with different semiconductors.