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Öğe N-type InP Schottky diodes with organic thin layer: Electrical and interfacial properties(Journal of Vacuum Science & Technology B, 2010-03) Güllü, Ömer; Turut, AbdulmecitThe rectifying junction characteristics of methyl red (MR) organic film on n-type InP substrate have been studied. It has been observed that MR-based structure shows an excellent rectifying behavior and that the MR film increases the effective barrier height by influencing the space charge region of the n-type InP. The barrier height and ideality factor values for this structure have been obtained as 0.75 eV and 1.93 from the forward bias current-voltage characteristics, respectively. By using capacitance-voltage characteristics at 1 MHz, the barrier height and the carrier concentration values have been calculated as 0.93 eV and 5.13×1015 cm−3, respectively. The energy distributions of the interface states and their relaxation times have been determined from the forward bias capacitance-frequency and conductance-frequency characteristics. Moreover, it was seen that both the interface-state density and the relaxation time of the interface states decreased with bias voltage from experimental results.Öğe Design of PV energy system in Batman Turkey(AIP Conf.Proc., 2017) Pakma, Nilay; Pakma, Osman; Güllü, ÖmerÖğe Control of barrier heigth ofmetal/semiconductor contacts bymolecular organic film(2011-06) Güllü, Ömer; Turut, Abdulmecit; Kılıçoğlu, Tahsin; Özerden, EniseÖğe Electronic properties of the Al/Orange G/n-Si junction(2017-04) Güllü, Ömer; Arsel, İsmailÖğe Some electrical parameters of the Sn/p-Si diode under γ-irradiation(Çukurova Üniversitesi, 2017) Pakma, Osman; Güllü, ÖmerThe radiation response of metal-semiconductor (MS) contacts has been found to alter significantly when the structures are exposed to pre-irradiation processes at determined doses. Radiation doses greater than a kilogray exposure may cause strong changes on the electrical characteristics of MS structures. It has been also shown that the particle or gamma irradiations induce defects in the band gap which affects the free carrier concentration and leads to an increase and decrease of barrier height in p-type and n-type semiconductors, respectively. The knowledge of the influence of radiation damage on the Schottky barrier diodes (SBDs) performance is a fundamental field of research, having technological relevance for many applications in the semiconductor electronic devices. Hence, it is very much essential to evaluate the effect of irradiation and identify the degradation mechanism to understand the failure mechanisms. In this work, we have investigated the electrical parameters of the Sn/p-Si Schottky barrier diodes by using I-V and C-V characteristics under γ-irradiation at room temperature. The basic diode parameters such as ideality factor, barrier height, series resistance and reverse saturation current were extracted from electrical measurements as a function of the irradiation dose. The results indicated that γ-irradiation induced an increase in the effective Schottky barrier height extracted from both I-V and C-V measurements. Also, it was seen that ideality factor increased with the increasing γ-irradiation doses. We have also observed that the reverse bias current of the Sn/Si contact exceedingly decreased with increasing irradiation dose with low energy (60 keV). The basic results as related to the gamma irradiation have been indicated that this device may have applications as radiation sensors in order to detect the low energy gamma radiation.Öğe Characterization of Au N Inp photovoltaic structure with organic thin film(Uppsala University, 2012) Güllü, Ömer; Özerden, Enise; Rüzgar, Şerif; Asubay, Sezai; Pakma, Osman; Kılıçoğlu, Tahsin; Türüt, AbdulmecitÖğe The effects of high-energy electron irradiation on the electrical characteristics of a lead/rhodamine-101/p-Si diode(Çukurova Üniversitesi, 2017) Güllü, Ömer; Pakma, OsmanHigh-energy radiation penetrates the metal-semiconductor (MS) interface and causes damage deep below the interface. Low-energy radiation causes severe lattice damage in the form of vacancies, interstitials and defect complexes at the near interface of the device. The one kind of the radiation is electron beam which is accelerated. Mills was the first to recognize that electrons with energy of 1 MeV would possess enough energy to displace an atom from its lattice position. This observation has led to the increased use of electron accelerators in radiation damage studies. This use has been motivated by two important facts. First, electron bombardment experiments permit the determination of the energy required to remove an atom from its initial position. This is done by increasing the energy of the electrons until an observable change in a radiation-sensitive property is seen. The second important basis for the use electrons lie in the fact that as long as the energy of the electrons is close to the displacement threshold, it is presumed, that only single Frenkel pairs are formed. Thus, many radiation-induced phenomena can be analyzed in terms of a single vacancy and/or interstitial atom, and one avoids the complication attendant upon the generation of complex damage regions presumed to occur in heavy-charged particle irradiation. In the present paper, a lead/rhodamine-101(Rh101)/p-Si metal/organic interlayer/ semi-conductor diode was fabricated and the effect of 6 MeV-electron irradiation on the electrical characteristics of the diode structure was investigated. It was seen that after electron irradiation the barrier height values, the series resistance values and ideality factors increased. Furthermore, it was seen that the capacitance values increased after electron irradiation. This was attributed to the change in dielectric constant at the interface and/or to decrease in the net ionized dopant concentration and the interface states. The degradation of the diode properties may be due to the introduction of electron irradiationinduced interfacial defects via displacement damage.Öğe Wet chemical methods for producing mixing crystalline phase ZrO 2 thin film(Elsevier, 2016-07) Pakma, Osman; Özdemir, Cengiz; Kariper, İshak Afşin; Özaydın, Cihat; Güllü, ÖmerThe aim of the study is to develop a more economical and easier method for obtaining ZrO 2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO 2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO 2 /p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.Öğe Electrical characteristics of the Al/Congo Red (CR)/p-Si semiconductor diodes(Dumlupınar Üniversitesi, 2015-05) Güllü, Ömer; Pakma, Osman; Turut, Abdulmecit; Arsel, İsmailIn this work, we have studied the electrical characteristics of the Al/CR/p-Si MIS Schottky structures formed by coating of the organic material directly on p-Si substrate. It has been seen that the CR thin film on the p-Si substrate has indicated a good rectifying behavior. The barrier height and the ideality factor of the device have been calculated from the I-V characteristic. We have also studied the suitability and possibility of the MIS diodes for use in barrier modification of Si MS diodes. In addition, we have compared the parameters of the Al/CR/p-Si MIS Schottky diodes with those of conventional Al/p-Si MS diodes. We have observed that the b value of 0.77 eV obtained for the Al/CR/p-Si device was significantly larger than BH value of the conventional Al/p-Si MS contact. Thus, the modification of the interfacial potential barrier for metal/Si diodes has been achieved by using the CR organic interlayer. This was attributed to the fact that the CR interlayer increased the effective b by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 eV-1 cm-2 to 2.44×1012 eV-1 cm-2.Öğe Morphological, structural and optical characteristics of graphene oxide layers and metal/interlayer/semiconductor photovoltaic diode application(National Institute of Research and Development for Optoelectronics, 2018) Güllü, Ömer; Çankaya, MuratThis work describes the optical, morphological and structural characterizations of graphene oxide (GO) layers grown by drop casting and annealing process. UV-vis optical measurement shows that the values of direct and indirect optical gap energy of the GO film are 3.89 eV and 3.21 eV, respectively. The graphene oxide (GO) layer has been placed in the metal/ interlayer /semiconductor (MIS) diodes (total 17 devices) on p-Si wafers. The graphene oxide diodes give a better barrier height enhancement as compared with the conventional diodes. The value of homogeneous barrier height for Al/GO/p-Si MIS junctions was extracted as 0.74 eV. The diodes were also investigated under 300 watt light illumination for photovoltaic applications. Additionally, interfacial properties of the MIS diode with GO interlayer were determined. It has been seen that the capacitance of the device changes as a function of gate voltage and signal frequency from the capacitance-frequency measurements. It has also been reported that the interfacial trap charges reduce the capacitance with increasing frequency values.
