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Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes
(Elsevier, 2008-03-25) Güllü, Ömer; Turut, Abdulmecit; Asubay, Sezai
We have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 °C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current–voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current–voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 °C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface.
Analysis of the series resistance and interface state densities in metal semiconductor structures
(Journal of Physics: Conference Series, 2009-03) Güllü, Ömer; Karataş, Şükrü; Güler, Gülşen; Bakkaloğlu, Ömer Faruk
The electrical properties of Co/n-Si metal-semiconductor (MS) Schottky structure investigated at room temperature using current-voltage (I-V) characteristics. The characteristic parameters of the structure such as barrier height, ideality factor and series resistance have been determined from the I-V measurements. The values of barrier height obtained from Norde’s function were compared with those from Cheung functions, and it was seen that there was a good agreement between barrier heights from both methods. The series resistance values calculated with Cheung’s two methods were compared and seen that there was an agreement with each other. However, the values of series resistance obtained from Cheung functions and Norde’s functions are not agreeing with each other. Because, Cheung functions are only applied to the non-linear region (high voltage region) of the forward bias I–V characteristics. Furthermore, the energy distribution of interface state density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The results show that the presence of thin interfacial layer between the metal and semiconductor
The analysis of the charge transport mechanism of n-Si/MEH-PPV device structure using forward bias I-V-T characteristics
(Elsevier, 2010-03-04) Kavasoğlu, Abdülkadir Sertap; Yakuphanoğlu, Fahrettin; Kavasoğlu, Neşe; Pakma, Osman; Birgi, Özcan; Oktik, Şener
In this study, temperature dependent current-voltage (I-V) measurements and investigation of the dc current transport mechanism of n-Si/MEH-PPV device have been performed. While the series resistance value displayed strongly temperature dependent behaviour, the ideality factor varied between 3.2 and 1.8 in the temperature range 110-330 K. The temperature dependent ideality factor behaviour at low temperature region (110-220 K) shows that tunnelling enhanced recombination is valid rather than thermionic emission theory and the characteristic tunnelling energy is calculated as 30 meV. There is a slightly linear relationship between the ideality factor and temperature at region II (230-330 K) which is attributed to drift-diffusion current transport in the n-Si/MEH-PPV device as stated already by Osvald.
The analysis of lateral distribution of barrier height in identically prepared Co/n-Si Schottky diodes
(Elsevier, 2009-11-03) Güllü, Ömer; Karataş, Şükrü; Güler, Gülşen; Bakkaloğlu, Ömer Faruk
We have studied the experimental linear relationship between ideality factors and barrier heights (BHs) for Co/n-Si metal–semiconductor (MS) structures with a doping density of about 1015 cm−3. The barrier heights for the Co/n-type Si metal–semiconductor structures from the current–voltage (I–V) characteristics varied from 0.64 to 0.70 eV, the ideality factor n varied from 1.18 to 1.26, and from reverse bias capacitance–voltage (C−2–V) characteristics the barrier height varied from 0.68 to 0.81 eV. The experimental barrier height distributions obtained from the I–V and C−2–V characteristics were fitted by a Gaussian distribution function, and their mean values were found to be 0.67 and 0.75 eV, respectively. Furthermore, the lateral homogeneous BH value of approximately 0.81 eV for Co/n-Si metal–semiconductor structures was obtained from the linear relationship between experimental effective BHs and ideality factors.
I-V-T analysing an inhomogeneous Au/Poly(4-vinyl phenol)/p-Si structure with a double gaussian distribution of barrier heights
(Springer Nature, 2010-12-29) Pakma, Osman; Tozlu, Cem; Kavasoğlu, Neşe; Kavasoğlu, Abdülkadir Sertap; Özden, Şadan
In this study, the current-voltage (I-V) characteristics of Au/Poly(4-vinyl phenol)/p-Si structures have been measured over a wide temperature range (100-300 K). These structures have been analyzed according to thermionic emission (TE) theory, as a result of which an abnormal decrease occurred in the zero-bias barrier height (φb0) and an increase in the ideality factor (n) was observed with temperature decrease and nonlinearity in the activation energy plot. By assuming a Gaussian distribution (GD) of barrier heights of the Au/Poly(4-vinyl phenol)/p-Si structures, barrier inhomogeneities are believed to responsible for this behavior. Evidence is given for the existence of a double GD with mean barrier heights (φ̄b0) of 1.042 and 0.623 eV, standard deviations of 0.138 and 0.081 V, and ideality factors 2.76 and 7.26, which remain effective in the temperature ranges of 180-300 and 100-160 K, respectively. As a result, without using the temperature coefficient of the barrier height, the modified ln(Io/T 2)-q2σo 2/2(kT)2 vs. q/kT plot gives φ̄b0 values and Richardson constants (A *) as 1.036 and 0.623 eV, and 36.20 and 19.99 A/cm2 K2, respectively. The effective Richardson constant value of 36.20 A/cm2 K2 is very similar to the theoretical value of 32 A/cm2K2 for p-Si. Consequently, the temperature dependence of the forward bias I-V characteristics of Au/Poly(4-vinyl phenol)//p-Si (MIS) structure could be attributed to the thermionic emission (TE) mechanism with double GD of the barrier heights.
On the energy distribution profile of interface states obtained by taking into account of series resistance in Al/TiO2/p–Si (MIS) structures
(Elsevier, 2011-02-15) Pakma, Osman; Serin, Necmi; Serin, Saliha Tülay; Altındal, Şemsettin
The energy distribution profile of the interface states (Nss) of Al/TiO2/pSi (MIS) structures prepared using the solgel method was obtained from the forward bias currentvoltage (IV) characteristics by taking into account both the bias dependence of the effective barrier height (φe) and series resistance (Rs) at room temperature. The main electrical parameters of the MIS structure such as ideality factor (n), zero-bias barrier height (φb0) and average series resistance values were found to be 1.69, 0.519 eV and 659 Ω, respectively. This high value of n was attributed to the presence of an interfacial insulator layer at the Al/pSi interface and the density of interface states (Nss) localized at the Si/TiO2 interface. The values of Nss localized at the Si/TiO2 interface were found with and without the Rs at 0.25-Ev in the range between 8.4×10 13 and 4.9×1013 eV-1 cm-2. In addition, the frequency dependence of capacitancevoltage (CV) and conductancevoltage (G/ω-V) characteristics of the structures have been investigated by taking into account the effect of Nss and R s at room temperature. It can be found out that the measured C and G/ω are strongly dependent on bias voltage and frequency.
Electrical characteristics of Co/n-Si schottky barrier diodes using I – V and C – V measurements electrical characteristics of Co/n-Si schottky barrier diodes using I – V and C – V measurements
(Chinese Physics Letters, 2009-06) Güllü, Ömer; Güler, Gülşen; Karataş, Şükrü; Bakkaloğlu, Ömer Faruk
Electrical characteristics of Co/n-Si Schottky barrier diodes are analysed by current-voltage (I – V) and capacitance-voltage (C – V) techniques at room temperature. The electronic parameters such as ideality factor, barrier height and average series resistance are determined. The barrier height 0.76eV obtained from the C – V measurements is higher than that of the value 0.70eV obtained from the I – V measurements. The series resistance RS and the ideality factor n are determined from the d ln(I)/dV plot and are found to be 193.62Ω, and 1.34, respectively. The barrier height and the RS value are calculated from the H(I) – I plot and are found to be 0.71 eV and 205.95Ω. Furthermore, the energy distribution of the interface state density is determined from the forward bias I – V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density Nss ranges from 6.484 × 1011 cm−2eV−1 in (EC – 0.446) eV to 2.801 × 1010 cm−2eV−1 in (EC – 0.631) eV, of the Co/n-Si Schottky barrier diode. The results show the presence of a thin interfacial layer between the metal and the semiconductor.
Current mechanism in HfO 2-gated metal-oxide-semiconductor devices
(Hindawi, 2012-06-19) Pakma, Osman
The present study aimed to examine the current density-voltage (J-V) characteristics of Al/HfO2/p-Si (MOS) structure at temperatures ranging between 100 and 320 K and to determine the structure’s current transport mechanism. The HfO2 film was coated on a single side of the p-Si (111) crystal using the spin coating method. The J-V measurements of the obtained structure at the temperatures between 100 and 320 K revealed that the current transport mechanism in the structure was compatible with the Schottky emission theory. The Schottky emission theory was also used to calculate the structure’s Schottky barrier heights (φB), dielectric constants (εr) and refractive index values of the thin films at each temperature value. The dielectric constant and refractive index values were observed to decrease at decreasing temperatures. The capacitance-voltage (C-V) and conductancevoltage (G/ω-V) characteristics of Al/HfO2/p-Si (MOS) structure was measured in the temperature range of 100–320 K. The values of measured C and G/ω decrease in accumulation and depletion regions with decreasing temperature due to localized Nss at Si/HfO2 interface.
Organik arayüzey tabakalı Al/CuPc /p-InP kontakların fabrikasyonu ve elektriksel parametrelerinin incelenmesi
(Batman Üniversitesi, 2015-07-01) Aslan, Filiz; Güllü, Ömer; Ocak, Yusuf Selim; Rüzgar, Şerif; Tombak, Ahmet; Özaydın, Cihat; Pakma, Osman; Arsel, İsmail
Bu çalışmada termal buharlaştırma metodu kullanılarak bakır fitalosiyanin (CuPc) p-InP kristali üzerine kaplandı. Yine termal buharlaştırma sistemi kullanılarak oluşan ince organik film üzerine vakum ortamında alüminyum metali kaplandı ve Al/CuPc/p-InP diyot yapısı oluşturuldu. Al/CuPc/p-InP diyotunun oda sıcaklığında, karanlık ve aydınlık ortamda akım-gerilim (I-V) ölçümleri alındı. I-V grafiğinden bu yapının doğrultucu özellik gösterdiği görüldü. Aydınlık ortamda yapılan ölçümler 100 mW/cm2 ışık şiddeti altında yapıldı ve bu ölçümler doğrultusunda diyotun fotodiyot özellik gösterdiği görüldü. Ayrıca farklı yöntemlerle Al/CuPc/p-InP Schottky diyotunun karakteristik parametreleri ( idealite faktörü (n) ,engel yüksekliği (Φb) ve seri direnç (Rs) ) hesaplandı.
Electrical properties of organic–ınorganic semiconductor device based on rhodamine-101
(SpringerLink, 2009-05) Güllü, Ömer; Turut, Abdulmecit; Yıldırım, Nezir; Çakar, Muzaffer
Rhodamine-101 (Rh101) thin films on n-type Si substrates have been formed by means of evaporation, thus Sn/Rh101/n-Si heterojunctions have been fabricated. The Sn/Rh101/n-Si devices are rectifying. The optical energy gaps have been determined from the absorption spectra in the wavelength range of 400 nm to 700 nm. Rh101 has been characterized by direct optical absorption with an optical edge at 2.05 ± 0.05 eV and by indirect optical absorption with␣an optical edge at 1.80 ± 0.05 eV. It was demonstrated that trap-charge-limited current is the dominant transport mechanism at large forward bias. A␣mobility value of μ = 7.31 × 10−6 cm2 V−1 s−1 for Rh101 has been obtained from the forward-bias current–voltage characteristics.
Electrical analysis of organic interlayer based metal/interlayer/semiconductor diode structures
(Journal of Applied Physics, 2009-01) Güllü, Ömer; Turut, Abdulmecit
In this work, metal/interlayer/semiconductor (MIS) diodes formed by coating of an organic film to p-Si semiconductor substrate were prepared. Metal(Al)/interlayer (phenolsulfonphthalein=PSP)/semiconductor(p-Si) MIS device had a good rectifying behavior. By using the forward bias I-V characteristics, the values of ideality factor (n) and barrier height (Phi(b)) for the Al/PSP/p-Si MIS diode were obtained as 1.45 and 0.81 eV, respectively. It was seen that the Phi(b) value of 0.81 eV calculated for the Al/PSP/p-Si MIS diode was significantly larger than value of 0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of Al/p-Si diode was achieved by using a thin interlayer of the PSP organic material. This has been attributed to the fact that the PSP organic interlayer increases the effective barrier height by influencing the space-charge region of Si. The interface-state density of the MIS diode was determined, and the interface-state density was found to vary from 3.00 x 10(13) to 2.99 x 10(12) eV(-1) cm(-2). (C) 2009 American Institute of Physics.
Ultrahigh (100%) barrier modification of n-InP Schottky diode by DNA biopolymer nanofilms
(Elsevier, 2010-04) Güllü, Ömer
Here I demonstrate that DNA biopolymer molecules can control the electrical characteristics of conventional Al/n-InP metal–semiconductor contacts. Results show that DNA increases an effective barrier height as high as 0.87 eV by influencing the space charge region of n-InP device with a good rectifying behavior
N-type InP Schottky diodes with organic thin layer: Electrical and interfacial properties
(Journal of Vacuum Science & Technology B, 2010-03) Güllü, Ömer; Turut, Abdulmecit
The 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.
A study of the rectifying behaviour of aniline green-based Schottky diode
(Elsevier, 2010-02) Güllü, Ömer; Aydoğan, Şakir
An Al/aniline green (AG)/Ga2Te3 device was fabricated and the current–voltage (I–V), capacitance–voltage (C–V) and capacitance–frequency (C–f) characteristics of the device have been investigated at room temperature. The values of the ideality factor, series resistance and barrier height obtained from Cheung and Norde methods were compared, and it was seen that there was an agreement with each other. It was seen that the forward bias current–voltage characteristics at sufficiently large voltages has shown the effect of the series resistance. In addition, it was seen from the C–f characteristics that the values of capacitance have been decreased towards to the high frequencies. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the Ga2Te3 that can follow the ac signal.
Silicon MIS diodes with Cr2O3 nanofilm Optical morphological structural and electronic transport properties
(Elsevier, 2010-04-15) Güllü, Ömer; Erdoğan, İbrahim Yasin
In this work we report the optical, morphological and structural characterization and diode application of Cr2O3 nanofilms grown on p-Si substrates by spin coating and annealing process. X-ray diffraction (XRD), non-contact mode atomic force microscopy (NC-AFM), ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) spectroscopy were used for characterization of nanofilms. For Cr2O3 nanofilms, the average particle size determined from XRD and NC-AFM measurements was approximately 70 nm. Structure analyses of nanofilms demonstrate that the single phase Cr2O3 on silicon substrate is of high a crystalline structure with a dominant in hexagonal (1 1 0) orientation. The morphologic analysis of the films indicates that the films formed from hexagonal nanoparticles are with low roughness and uniform. UV–vis absorption measurements indicate that the band gap of the Cr2O3 film is 3.08 eV. The PL measurement shows that the Cr2O3 nanofilm has a strong and narrow ultraviolet emission, which facilitates potential applications in future photoelectric nanodevices. Au/Cr2O3/p-Si metal/interlayer/semiconductor (MIS) diodes were fabricated for investigation of the electronic properties such as current–voltage and capacitance–voltage. Ideality factor and barrier height for Au//Cr2O3/p-Si diode were calculated as 2.15 eV and 0.74 eV, respectively. Also, interfacial state properties of the MIS diode were determined. The interface-state density of the MIS diode was found to vary from 2.90 × 1013 eV−1 cm−2 to 8.45 × 1012 eV−1 cm−2.
Electronic properties of the metal organic interlayer inorganic semiconductor sandwich device
(Elsevier, 2010-03) Güllü, Ömer; Turut, Abdulmecit; Kılıçoğlu, Tahsin
In this study, we prepared a Metal(Al)/Organic Interlayer(Congo Red=CR)/Inorganic Semiconductor (p-Si) (MIS) Schottky device formed by coating of an organic film on p-Si semiconductor wafer. The Al/CR/p-Si MIS device had a good rectifying behavior. By using the forward bias I–V characteristics, the values of ideality factor (n) and barrier height (Φb) for the Al/CR/p-Si MIS device were obtained as 1.68 and 0.77 eV, respectively. It was seen that the Φb value of 0.77 eV calculated for the Al/CR/p-Si MIS device was significantly higher than value of 0.50 eV of the conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of the Al/p-Si diode was achieved by using a thin interlayer of the CR organic material. This was attributed to the fact that the CR organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 to 2.44×1012 eV−1 cm−2.
Optical and structural properties of CuO nanofilm Its diode application
(Elsevier, 2010-03-04) Güllü, Ömer; Erdoğan, İbrahim Yasin
The high crystalline CuO nanofilms have been prepared by spin coating and annealing combined with a simple chemical method. The obtained films have been characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–vis (UV–vis) spectroscopy and photoluminescence (PL) spectroscopy. Structural analysis results demonstrate that the single phase CuO on Si (1 0 0) substrate is of high a crystalline structure with a dominant in monoclinic (1 1 1) orientation. FT-IR results confirm the formation of pure CuO phase. UV–vis absorption measurements indicate that the band gap of the CuO films is 2.64 eV. The PL spectrum of the CuO films shows a broad emission band centered at 467 nm, which is consistent with absorption measurement. Also, Au/CuO/p-Si metal/interlayer/semiconductor (MIS) diodes have been fabricated. Electronic properties (current–voltage) of these structures were investigated. In addition, the interfacial state properties of the MIS diode were obtained. The interface-state density of the MIS diode was found to vary from 6.21 × 1012 to 1.62 × 1012 eV−1 cm−2.
Temperature dependent electrical transport in Al/Poly(4-vinyl phenol)/ p -GaAs metal-oxide-semiconductor by sol-gel spin coating method
(Hindawi, 2016-03-10) Özden, Şadan; Tozlu, Cem; Pakma, Osman
Deposition of poly(4-vinyl phenol) insulator layer is carried out by applying the spin coating technique onto p-type GaAs substrate so as to create Al/poly(4-vinyl phenol)/p-GaAs metal-oxide-semiconductor (MOS) structure. Temperature was set to 80-320 K while the current-voltage (I-V) characteristics of the structure were examined in the study. Ideality factor (n) and barrier height (φ b) values found in the experiment ranged from 3.13 and 0.616 eV (320 K) to 11.56 and 0.147 eV (80 K). Comparing the thermionic field emission theory and thermionic emission theory, the temperature dependent ideality factor behavior displayed that thermionic field emission theory is more valid than the latter. The calculated tunneling energy was 96 meV.
Interface effects of annealing temperatures in Al/HfO2/p-Si (MIS) structures
(Gazi Üniversitesi, 2017-09-20) Özden, Şadan; Pakma, Osman
In this study, Al/HfO2/p-Si (MIS) structures were prepared by using the sol-gel method for three different annealing temperatures. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of these structures were investigated by taking into consideration the effect of the interfacial insulator layer and surface states (Nss) at room temperature. All of the structures showed non-ideal I-V behaviour with ideality factor (n) in the range between 2.35 and 4.42 owing to interfacial insulator layer and surface states. The values of Nss and barrier height (fb) for three samples were calculated. The values of n and Nss ascend with increasing the insulator layer thickness (δ) while the values of fb decreases.
Improvement of diode parameters in Al/n-Si schottky diodes with coronene interlayer using variation of the illumination intensity
(Elsevier, 2017-12-15) Pakma, Osman; Çavdar, Şükrü; Koralay, Haluk; Tuğluoğlu, Nihat; Yüksel, Ömer Faruk
In present work, Coronene thin films on Si wafer have been deposited by the spin coating method. It has been ultimately produced Al/Coronene/n-Si/In Schottky diode. Current–voltage (I-V) measurements have been used to determine the effect of illumination intensity in the Schottky diodes. The barrier height (ΦB) values increased as ideality factor (n) values decreased with a increase in illumination intensity. The ΦB values have been found to be 0.697 and 0.755 eV at dark and 100 mW/cm2, respectively. The n values have been found to be 2.81 and 2.07 at dark and 100 mW/cm2, respectively. Additionally, the series resistance (Rs) values from modified Norde method and interface state density (Nss) values using current-voltage measurements have been determined. The values of Rs have been found to be 1924 and 5094 Ω at dark and 100 mW/cm2, respectively. The values of Nss have been found to be 4.76 × 1012 and 3.15 × 1012 eV−1 cm−2 at dark and 100 mW/cm2, respectively. The diode parameters are improved by applying the variation of illumination intensity to the formed Schottky diodes.

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