Güllü, Hasan Hüseyin
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Name Variants
Gullu,H.H.
H.,Güllü
H.H.Güllü
G., Hasan Huseyin
Güllü, Hasan Hüseyin
H., Gullu
G.,Hasan Huseyin
H.H.Gullu
Hasan Hüseyin, Güllü
G.,Hasan Hüseyin
Hasan Huseyin, Gullu
Gullu, Hasan Huseyin
Güllü,H.H.
Gullu, H. H.
Gullu, Hasan H.
H.,Güllü
H.H.Güllü
G., Hasan Huseyin
Güllü, Hasan Hüseyin
H., Gullu
G.,Hasan Huseyin
H.H.Gullu
Hasan Hüseyin, Güllü
G.,Hasan Hüseyin
Hasan Huseyin, Gullu
Gullu, Hasan Huseyin
Güllü,H.H.
Gullu, H. H.
Gullu, Hasan H.
Job Title
Doktor Öğretim Üyesi
Email Address
hasan.gullu@atilim.edu.tr
Main Affiliation
Department of Electrical & Electronics Engineering
Status
Former Staff
Website
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
2
ZERO HUNGER
0
Research Products
14
LIFE BELOW WATER
0
Research Products
17
PARTNERSHIPS FOR THE GOALS
0
Research Products
5
GENDER EQUALITY
0
Research Products
16
PEACE, JUSTICE AND STRONG INSTITUTIONS
0
Research Products
8
DECENT WORK AND ECONOMIC GROWTH
0
Research Products
4
QUALITY EDUCATION
0
Research Products
6
CLEAN WATER AND SANITATION
0
Research Products
7
AFFORDABLE AND CLEAN ENERGY
5
Research Products
10
REDUCED INEQUALITIES
0
Research Products
11
SUSTAINABLE CITIES AND COMMUNITIES
0
Research Products
9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
0
Research Products
1
NO POVERTY
0
Research Products
3
GOOD HEALTH AND WELL-BEING
0
Research Products
12
RESPONSIBLE CONSUMPTION AND PRODUCTION
0
Research Products
13
CLIMATE ACTION
0
Research Products
15
LIFE ON LAND
0
Research Products
This researcher does not have a Scopus ID.
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Scholarly Output
55
Articles
52
Views / Downloads
7/0
Supervised MSc Theses
1
Supervised PhD Theses
0
WoS Citation Count
877
Scopus Citation Count
899
WoS h-index
16
Scopus h-index
16
Patents
0
Projects
0
WoS Citations per Publication
15.95
Scopus Citations per Publication
16.35
Open Access Source
8
Supervised Theses
1
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| Journal | Count |
|---|---|
| Journal of Materials Science: Materials in Electronics | 16 |
| Physica B: Condensed Matter | 7 |
| Bulletin of Materials Science | 3 |
| Materials Science in Semiconductor Processing | 3 |
| Optik | 3 |
Current Page: 1 / 5
Scopus Quartile Distribution
Competency Cloud
10 results
Scholarly Output Search Results
Now showing 1 - 10 of 10
Article Citation - WoS: 13Citation - Scopus: 15Investigation of electrical characteristics of Ag/ZnO/Si sandwich structure(Springer, 2019) Gullu, H. H.; Surucu, O. Bayrakli; Terlemezoglu, M.; Yildiz, D. E.; Parlak, M.In this study, temperature-dependent current-voltage (I-V), frequency-dependent capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements are carried out for the electrical characterization of a zinc oxide (ZnO) thin film-based diode. The sandwich structure in the form of Ag/ZnO/Si/Al is investigated at temperatures between 220 and 360 K and in the frequency region of 1 kHz-1 MHz. ZnO thin film layer is deposited on a p-Si wafer substrate as a transparent conductive oxide layer by taking into consideration possible electronic applications with intrinsic attractive material properties. At each temperature step, the I-V curves showed about two orders of magnitude rectifying behavior and, according to the Schottky diode relation, the saturation current, zero-bias barrier height and ideality factor were extracted as a function of the temperature. In the case of non-ideal diode characteristics due to the inhomogeneties in the diode as observed from the characteristics of the calculated parameters, effective barrier height values are evaluated. In addition, based on the existence of the interface layer, density of interface states in the band gap region and parasitic resistances were determined by the capacitance measurements.Article Citation - WoS: 17Citation - Scopus: 18Investigation of Band Gap Energy Versus Temperature for Sns 2 Thin Films Grown by Rf-Magnetron Sputtering(Elsevier, 2020) Isik, M.; Gullu, H. H.; Terlemezoglu, M.; Surucu, O. Bayrakli; Parlak, M.; Gasanly, N. M.[No Abstract Available]Article Citation - WoS: 10Citation - Scopus: 10Cztsse Thin Films Fabricated by Single Step Deposition for Superstrate Solar Cell Applications(Springer, 2019) Terlemezoglu, M.; Surucu, O. Bayrakli; Dogru, C.; Gullu, H. H.; Ciftpinar, E. H.; Ercelebi, C.; Parlak, M.The focus of this study is the characterization of Cu2ZnSn(S,Se)(4) (CZTSSe) thin films and fabrication of CZTSSe solar cell in superstrate configuration. In this work, superstrate-type configuration of glass/ITO/CdS/CZTSSe/Au was entirely fabricated by totally vacuum-based process. CZTSSe absorber layers were grown by RF magnetron sputtering technique using stacked layer procedure. SnS, CuSe and ZnSe solid targets were used as precursors and no additional step like the selenization process was applied. The structural and morphological properties of deposited CZTSSe layers were analyzed using X-ray diffraction (XRD), Raman scattering, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analysis (EDS) measurements. The optical and electrical properties of the CZTSSe thin films were investigated by UV-Vis spectroscopy, Hall-Effect and photoconductivity measurements. In addition, the device performance of the fabricated superstrate solar cell was examined.Article Citation - WoS: 3Citation - Scopus: 4Analysis of Temperature-Dependent Transmittance Spectra of Zn0.5in0.5< (zis) Thin Films(Springer, 2019) Isik, M.; Gullu, H. H.; Delice, S.; Gasanly, N. M.; Parlak, M.Temperature-dependent transmission experiments of ZnInSe thin films deposited by thermal evaporation method were performed in the spectral range of 550-950nm and in temperature range of 10-300K. Transmission spectra shifted towards higher wavelengths (lower energies) with increasing temperature. Transmission data were analyzed using Tauc relation and derivative spectroscopy. Analysis with Tauc relation was resulted in three different energy levels for the room temperature band gap values of material as 1.594, 1.735 and 1.830eV. The spectrum of first wavelength derivative of transmittance exhibited two maxima positions at 1.632 and 1.814eV and one minima around 1.741eV. The determined energies from both methods were in good agreement with each other. The presence of three band gap energy levels were associated to valence band splitting due to crystal-field and spin-orbit splitting. Temperature dependence of the band gap energies were also analyzed using Varshni relation and gap energy value at absolute zero and the rate of change of gap energy with temperature were determined.Article Citation - WoS: 16Citation - Scopus: 16Frequency Effect on Electrical and Dielectric Characteristics of In/Cu2< Diode Structure(Springer, 2019) Gullu, H. H.; Surucu, O. Bayrakli; Terlemezoglu, M.; Yildiz, D. E.; Parlak, M.In/Cu2ZnSnTe4/Si/Ag diode structure was fabricated by sputtering Cu2ZnSnTe4 (CZTTe) thin film layer on the Si layer with In front contact. The frequency dependent room temperature capacitance and conductance measurements were carried out to obtain detailed information of its electrical characteristics. Admittance spectra of the diode exhibited strong frequency dependence and the obtained values showed decreasing behavior with the increase in the applied frequency. The effect of interfacial film layer with series resistance values and density of interface states were investigated by taking into consideration of non-ideal electrical characteristics of the diode. The distribution profile of the interface states was extracted by Hill-Coleman and high-low frequency capacitance methods. As a function of frequency, they were in proportionality with the inverse of applied frequency. Dielectric constant and dielectric loss parameters were calculated from the maximum value of the diode capacitance at the strong accumulation region. The loss tangent showed a characteristic peak behavior at each frequency. Based on the time-dependent response of the interfacial charges to the applied ac field, the values of ac electrical conductivity and complex electric modulus were calculated and discussed as a function of frequency and bias voltage.Article Citation - WoS: 12Citation - Scopus: 12Material and Si-based diode analyses of sputtered ZnTe thin films(Springer, 2020) Gullu, H. H.; Surucu, O. Bayrakli; Isik, M.; Terlemezoglu, M.; Parlak, M.Structural, optical, and electrical properties ZnTe thin films grown by magnetron sputtering technique were studied by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and electrical conductivity measurements. Structural analyses showed that ZnTe thin films grown on soda-lime glass substrates have a cubic crystalline structure. This crystalline nature of the films was also discussed in terms of Raman active modes. From atomic force microscopy images, the smooth and dense surface profile was observed. The conductivity of the film at room temperature was measured as 2.45 x 10(-4)(omega cm)(-1)and the temperature dependency of conductivity showed Arrhenius behavior. The dark conductivity profile was modeled by thermionic emission mechanism and activation energies were extracted. In addition, the conductivity values indicated an increasing behavior with illumination intensity applied between 20 and 115 mW/cm(2). The heterojunction diode was generated by sputtering ZnTe film on n-Si wafer substrate and the rectification behavior was evaluated to determine the main diode parameters.Article Citation - WoS: 6Citation - Scopus: 6Temperature Dependence of Electrical Properties in Cu0.5ag0.5< Heterostructure(Springer, 2018) Gullu, H. H.; Parlak, M.The polycrystalline Cu0.5Ag0.5InSe2 thin film was deposited on mono-crystalline n-Si wafer by sequential thermal evaporation of elemental sources. p-Cu0.5Ag0.5InSe2/n-Si heterojunction diode was fabricated and the current-voltage characteristics of the diode at various temperatures were investigated to determine the main diode parameters and dark current transport mechanism. The studied diode structure showed a rectifying behavior with a barrier height of 0.63 eV at room temperature. Series and shunt resistance values were calculated by parasitic resistance relations in high bias regions. Considering the ideality factor values between 1.7 and 2.8, dominant transport characteristics were detailed for forward and reverse voltages. The analysis of the forward current-voltage behavior reveals field emission can be the possible current conduction mechanism. At the reverse bias region, around 10(1) number of tunneling step and about 10(5) density of traps were found to act a role in the process in leakage current flow.Article Citation - WoS: 31Citation - Scopus: 31Frequency Effect on Electrical and Dielectric Characteristics of Hfo2-interlayered Si-Based Schottky Barrier Diode(Springer, 2020) Gullu, H. H.; Yildiz, D. E.; Surucu, O.; Parlak, M.This study reveals the electrical properties of In/HfO2/n-Si structure with atomic layer-deposited interfacial oxide layer, HfO2 thin film between In top metal contact and monocrystalline Si wafer substrate. From the dark current-voltage measurements, the diode structure showed good rectifying behavior and low saturation current of about two order of magnitude and 1.2 x 10(- 9) A, respectively. According to the conventional thermionic emission model, zero-bias barrier height and ideality factor were calculated from the forward bias current-voltage curve at room temperature under dark conditions as 0.79 eV and 4.22 eV, respectively. In order to get detailed information about density of interface states and series resistance of this structure, capacitance-voltage and conductance-voltage measurements in the frequency range of 10-1000 kHz were performed. As a result, a decreasing capacitance profile with increasing frequency was obtained. In addition, peak-like behavior in the capacitance profiles was observed and these were found to be the indication of density of states. Further analysis was performed on the evaluation of density of interface states values and these values were calculated by using two different methods: Hill-Coleman and high-low frequency capacitance. These profiles were also analyzed by eliminating the effect of series resistance values on the measured capacitance and conductance; then the values of corrected capacitance and conductance as a function of applied voltage were discussed. Based on these analyses on the capacitive characteristics of the diode, dielectric constant, dielectric loss, loss tangent, electrical conductivity, and the real and imaginary part of electric modulus were investigated for complete understanding on the diode characteristics.Article Citation - WoS: 9Citation - Scopus: 9Effects of Si Nanowire on the Device Properties of N-znse/P-si Heterostructure(Springer, 2019) Coskun, E.; Gullu, H. H.; Colakoglu, T.; Emir, C.; Bozdogan, E.; Parlak, M.The semiconductor nanowire (NW) technology has raised attention owing to its one-dimensional geometry as a solution for lattice mismatch in the fabricated heterostructures. Although, SiNWs have been investigated for various device technologies, there is no published work on the p-n junction formed by deposition of ZnSe thin film on these NW structures, in which this film layer has significant optical and electrical properties in optoelectronics applications. The aim of this study is determining the device properties of n-ZnSe/SiNW heterojunction and obtaining the enhancement in the device application of the NW structure on Si surface with comparing to planar surface. SiNW was produced by metal assisted etching method as a cost-efficient process, and the ZnSe film was deposited on SiNW and planar Si substrates by thermal evaporation of elemental sources. The optical band gap of the deposited ZnSe film was determined as 2.7eV which is in a good agreement with literature. The ideality factor and series resistance values of the ZnSe/SiNW and ZnSe/Si heterojunctions were calculated as 3.12, 461 , and 4.52, 7.26x103, respectively. As a result of utilizing SiNW structure, a spectacular improvement in terms of the physical parameters related to device properties was achieved.Article Citation - Scopus: 2Material and Device Properties of Si-Based Cu0.5ag0.5< Thin-Film Heterojunction Diode(Springer, 2020) Gullu, H. H.; Isik, M.; Delice, S.; Parlak, M.; Gasanly, N. M.Cu0.5Ag0.5InSe2 (CAIS) thin films were deposited on a glass substrate by sequential sputtering of Cu, Ag, and In2Se3-stacked film layers. Structural characterization showed that the deposited CAIS film satisfies nearly the stoichiometric form with uniform and homogeneous surface structure. The single-phase polycrystalline behavior without any secondary-phase formation was observed from the diffraction profile. The optical properties were investigated using temperature-dependent transmission measurements in the wavelength region of 600-1100 nm and in between 10 and 300 K. In the region of interest, the transmission spectra shifted towards the higher wavelengths as a result of an increase in the sample temperature. The analysis of the absorption data based on the transmission spectra resulted in absorption coefficient values of around 10(5) cm(-1) and the presence of direct allowed optical transition. From the Tauc plots, CAIS samples were found to have three distinct direct optical transitions depending on the possible splitting in the valence band. The obtained room temperature uppermost band gap energy value of 1.09 eV was found in the energy limit of ternary analogues (CuInSe2 and AgInSe2), and also in a good agreement with the previous works in the literature. The dependency of the band gap energy on the temperature was analyzed using fundamental relations. In addition, the electrical characteristics of the film layer were discussed in four-contact conductivity measurements, and room temperature conductivity was observed as 0.8 ohm(-1) cm(-1). Additionally, two activation energy values were found in the temperature-dependent conductivity profile. As a diode application, CAIS/Si heterojunction was fabricated and the main diode parameters were extracted at dark and room temperature conditions.
