İkram Orak

Investigation of Electrical Characteristics in Al/CdS-PVA/p-Si (MPS) Structures Using Impedance Spectroscopy Method

The cadmium sulfide (CdS) nanopowders have been prepared by ball-milling method, and CdS-polyvinyl alcohol (PVA) nanocompound in the form of film has been deposited on a p-Si wafer as an interfacial layer by spin-coating method. The impedance characteristics of the fabricated Al/CdS-PVA/ p-Si (metal-polymer-semiconductor)-type structures were studied in the frequency and voltage range of 5 kHz-5 MHz and ±1 V, respectively, by considering interface states (D_it), series resistance (R_s), and interfacial layer effects at 300 K. While the voltage and frequency dependence profiles of D_it were evaluated from the low-high frequency capacitance (C_LF-C_HF) and Hill-Coleman methods, R_s profiles were evaluated from the Nicollian and Brews method. Doping concentration atoms (N_A) and barrier height [Φ_B(capacitance-voltage (C-V))] values were also obtained from the reverse bias C-2 versus V plots for each frequency. While D_it and R_s values decrease with increasing frequency almost exponentially, Φ_B(C-V) increases linearly. Therefore, both the measured capacitance (C_m) and conductance (G_m/w) values were corrected to eliminate the R_s effect. The experimental results show that R_s value is more effective on the impedance measurements at high frequencies in the accumulation region, but D_it is effective at low frequencies in the depletion region.

Electrical characterizations of Au/ZnO/n-GaAs Schottky diodes under distinct illumination intensities

The Au/ZnO/n-GaAs Schottky barrier diode was fabricated and examined regarding to its current–voltage characteristics under distinct illumination intensities at room temperature. The reverse biased current increases with increasing illumination level while forward biased current is almost unchanged with illumination which states that the fabricated diodes exhibit photosensitive character or photodiode behavior. Hence, the shunt resistance is decreased with illumination while the series resistance is almost remained constant. The increment in the ideality factor after illumination can be ascribed to the assumption of inhomogeneities at M/S interface. Considering the ideality factor and the voltage dependent effective barrier height, the energy distribution profiles of surface states (Nss) were formed by the forward bias current–voltage data and increased with increasing illumination level. The Nss values acquired by considering series resistance are lower than those acquired by ignoring series resistance. Consequently, surface states can serve as recombination centers and have great importance especially in reverse bias current–voltage characteristics.

Electrical characteristics of Au/n-Si (MS) Schottky Diodes (SDs) with and without different rates (graphene + Ca1.9Pr0.1Co4Ox-doped poly(vinyl alcohol)) interfacial layer

In order to see effects of interfacial (with and without different graphene (GP) + Ca1.9Pr0.1Co4Ox-doped PVA) layer on the electrical characteristics of conventional Au/n-Si (MS) contacts. Therefore, Au/(GP + Ca1.9Pr0.1Co4Ox-doped PVA)/n-Si (MPS) structures were fabricated with different rates of (%3 GP, %7 GP) PVA and were fabricated on same n-Si wafer. Au/n-Si (MS), Au/PVA/n-Si, Au/%3GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si and Au/%7GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si structures were fabricated and their main electrical characteristics compared each other by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of with and without GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si at room temperature were studied to investigate its main electrical parameters. The energy density distribution profile of the interface states (Nss) was obtained from the forward bias I–V data by taking into account voltage dependent ideality factor (n(v)) and effective barrier height (Φe) and they increase from at about mid-gap energy of Si to bottom of conductance band edge. In addition, voltage dependent profile of resistivity of the structure was obtained from I–V data for four different structures. The analysis of experimental results reveals that the existence of GP + Ca1.9Pr0.1Co4Ox-doped PVA interfacial layer improves the performance of MS structure. In order to determine the dominant current-transport mechanism (CTM) in the whole forward bias region of these structures, the double logarithmic forward bias I–V plots were also drawn. These plots exhibit two distinct linear region with different slopes which are corresponding to intermediate and high forward bias voltages. The slope of these plots show that in the region 1 (low biases) the dominant CTM is trap-charge-limited current (TCLC), whereas in the region 2 (high biases) is space-charge-limited current (SCLC) for four diodes.

Memristive behavior in a junctionless flash memory cell

We report charge storage based memristive operation of a junctionless thin film flash memory cell when it is operated as a two terminal device by grounding the gate. Unlike memristors based on nanoionics, the presented device mode, which we refer to as the flashristor mode, potentially allows greater control over the memristive properties, allowing rational design. The mode is demonstrated using a depletion type n-channel ZnO transistor grown by atomic layer deposition (ALD), with HfO2 as the tunnel dielectric, Al2O3 as the control dielectric, and non-stoichiometric silicon nitride as the charge storage layer. The device exhibits the pinched hysteresis of a memristor and in the unoptimized device, Roff/Ron ratios of about 3 are presented with low operating voltages below 5 V. A simplified model predicts Roff/Ron ratios can be improved significantly by adjusting the native threshold voltage of the devices. The repeatability of the resistive switching is excellent and devices exhibit 106 s retention time, w...

Illumination impact on the electrical characterizations of an Al/Azure A/p-Si heterojunction

In this study, we fabricated an Al/Azure A/p-Si heterojunction. The electrical characterization and photovoltaic properties of the Al/Azure A/p-Si heterojunction were investigated by current–voltage (I–V) under dark and illuminated conditions at room temperature. The photovoltaic device gives Voc = 340 mV and Isc = 807 μA under 30 mW cm−2. The device was found to have a fill factor (FF) and power conversion efficiency (ηP) 36% and 4.07%, respectively. The values of some diode parameters were determined using thermionic emission theory. Some diode parameters, such as the ideality factor (n) and barrier height (b) values, were found to be 1.26 and 0.78 eV, respectively. An ideality factor higher than 1 can be explained on the basis of the inhomogeneity barrier-height model or as a result of natural oxide layers. The results obtained from electrical and photovoltaic properties show that the device can be used as photodiode and in opto-electronic circuit applications.

Frequency dependent electrical characteristics and origin of anomalous capacitance–voltage ( C–V ) peak in Au/(graphene-doped PVA)/n-Si capacitors

Au/(7% graphene-doped PVA)/n-Si capacitors were fabricated and their electrical characteristics were investigated using complex impedance spectroscopy method (ISM) in the wide frequency range at room temperature. Experimental results show that the values of capacitance (C) and conductance (G/ω) decrease with increasing frequency. Such behavior of these parameters, especially at low frequencies, was attributed to the surface polarization; surface states (Nss) and their relaxation time (τ). Main electrical parameters such as doping concentration of donor atoms (ND) and barrier height (ΦB(C–V)) were obtained from the reverse bias C−2–V plots for various frequencies. While the value of ND decreases, ΦB(C–V) increases with increasing frequency. The large values of C especially at low frequencies were attributed to the high dielectric graphene-doped PVA. C–V plots in depletion region show a distinctive anomalous peak such that its intensity increases with increasing frequency whereas its position shifts toward negative biases due to the effects Nss and series resistance (Rs). The plots of Nss versus V and Rs versus V are also obtained using low–high frequency capacitance (CLF–CHF) and Nicollian and Brews methods, respectively. Obtained results are promising considering the performance of capacitors in storing large amounts of charge, thus 7% graphene-doped PVA can be used as an alternative material for replacement of conventional silicon dioxide (SiO2).

The Analysis of the Electrical and Photovoltaic Properties of Cr/p-Si Structures Using Current-Voltage Measurements

In this work, the electrical and photovoltaic properties of Cr/p -Si structures were investigated using forward and reverse bias current-voltage (I - V ) measurements in dark and under illumination conditions (100 mW/cm2) at room temperature. The forward and reverse bias current–voltage (I - V ) characteristics of the Cr/p-Si structures were analyzed by the thermionic emission theory. For this, the main parameters such as ideality factors (n), barrier heights (Φbo), series resistances (RS), and reverse-saturation currents obtained from different methods using forward and reverse bias I - V measurements were investigated in under dark and illumination conditions at room temperature, respectively. Furthermore, the photovoltaic parameters such as short circuit current (Isc), open circuit voltage (Voc), fill factor (FF) and conversion efficiency (ηP) were acquired as 7.43 × 10-3 A/cm2, 0.260 V, 61.5% and 1.18% under 100 mW/cm2 light intensity, respectively, and these values are near to a photodiode. Experimental results show that all electrical parameters were found to be strong function of illumination density. Also, this result confirms that Cr/p-type-Si diode can be used as a photodiode in optoelectronic applications.

Preparation and characterization of cross-linked poly (vinyl alcohol)-graphene oxide nanocomposites as an interlayer for Schottky barrier diodes

Cross-linked polyvinyl alcohol (PVA) graphene oxide (GO) nanocomposites were prepared by simple solution-mixing route and characterized by Raman, UV–visible and fourier transform infrared (FT-IR) spectroscopy analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern and SEM analysis showed significant changes in the nanocomposite structures, and the FT-IR spectroscopy results confirmed the chemical interaction between the GO filler and the PVA matrix. After these morphological characterizations, PVA-GO-based diodes were fabricated and their electrical properties were characterized using current–voltage (I–V) and impedance-voltage-frequency (Z-V-f) measurements at room temperature. Semilogarithmic I–V characteristics of diode showed a good rectifier behavior. The values of C and G/ω increased with decreasing frequency due to the surface/interface states (Nss) which depend on the relaxation time and the frequency of the signal. The voltage, dependent profiles of Ns...

The thickness effect of insulator layer between the semiconductor and metal contact on C-V characteristics of Al/Si3N4/p-Si device

Öz Metal-insulator-semiconductor (MIS) structures have great interest for their good applications in electronic and optoelectronic. Their importance can be attributed that they have storage layer property, capacitance effect and high dielectric constant. For this reason, two samples of Si3N4 layers were deposited with plasma-enhanced chemical vapor deposition (PECVD) technique on p-type Si; first is about 5 nm thickness and the other is about 50 nm. The thicknesses of Si3N4 were adjusted by an ellipsometer. The thickness effect of Si3N4 layers on the Al/Si3N4/p type Si contact was studied with the capacitance-voltage (C–V) and conductance–voltage (G-V) characteristics of the contact at the frequency range from 10 kHz to 1 MHz and applied bias voltage from −5 V to +5 V at room temperature. In each contact having different insulator layers, capacitance values decreased and conductance values increased with increasing frequencies. The interface states (Nss), the effect of series resistance (Rs), barrier height (Φb) and carrier concentration (Na) were found from the capacitance-voltage (C–V) and conductance–voltage (G-V) measurements and explained in the details. To determine memristor behavior of the Al/Si3N4/p type Si contact, dual C-V and G-V measurements were performed at 500 kHz and the room temperature, and the results were compared for 5 nm and 50 nm thicknesses layers. Consequently, changing of Si3N4 layer thickness influenced properties of the contacts, and these two contacts have memristor behavior and, they can be used and improved as memory devices in the future. Metal-Yalıtkan-Yarıiletken (MIS) yapılar elektronik ve optoelektronikteki iyi uygulamalarından büyük ilgiye sahiptirler. Bu yapıların önemi tabaka depolama özelliği, kapasitans etkisi ve yüksek dileketrik sabitlerine sahip olmalarına dayandırılabilir. Bu yüzden Si3N4 tabakalı iki adet numune plazma destekli kimyasal buhar biriktirme (PECVD) yöntemiyle birinin kalınlığı 5 nm diğerinin kalınlığı 50 nm olacak şekilde p-tip Si üzerine büyütüldü. Si3N4 tabakasının kalınlığı bir elipsometreyle kontrol edildi. Al/Si3N4/p tip Si kontağın üzerine Si3N4 tabakasının kalınlık etkisi 10 kHz-1 MHz frekans değerleri için -5 V’tan +5 V voltaj aralığında yapıların kapasitans-voltaj (C–V) ve iletkenlik-voltaj (G–V) karakteristikleri ile oda sıcaklığında araştırıldı. Farklı kalınlığa sahip kontakların her bir durumda kapasitans değerlerinin artan frekansla azaldığı ve iletkenlik değerlerinin arttığı tespit edildi. Ara yüzey durumları (Nss) ve Seri direnç (Rs) etkileri, bariyer yüksekliği (Φb) ve taşıyıcı yoğunluğu (Na) kapasitans-voltaj (C–V) ve iletkenlik-voltaj (G–V) karakteristikleri karakterizasyonlardan elde edildi ve açıklandı. Ayrıca 5 nm ve 50 nm kalınlık değerindeki tabakalar için 500 kHz frekansta çift yönlü C-V ve G-V karakterizasyonlarından elde edildi ve kıyaslandı. Sonuç olarak, Si3N4 tabakasının kalınlık değişiminin kontakların özelliklerini etkilediği görüldü ve bu kontakların Memrezistör yapısına sahiptirler ve gelecekte hafıza aygıtları için kullanılabilir ve geliştirilebilirler.

The Effects of Thermal Annealing and Sample Temperature on Current-Voltage Characteristics of Au/n-Si/Al Schottky Diodes

Gunumuz elektronik teknolojisinde ve elektronik sanayinde cok fazla kullanilan Schottky kontaklar genis bir uygulama alanina ve onemli bir yere sahiptir. Bu sebeple bu elemanlar uzerinde cok fazla durulmasi gerekir ve bircok arastirmanin da konusu olmustur. Diyodun tavlama ve numune sicakligiyla karakteristik parametrelerinin degisip degismediginin degisimini gormek icin diyotlarin tavlamaya ve numune sicakligina bagli akim-gerilim karakteristikleri incelendi. Yapilan hesaplamalar sonucunda tavlanmamis diyot icin oda sicakliginda idealite faktoru ve engel yuksekligi I-V olcumlerinden sirasiyla 1,15 ve 0,74 eV degerleri elde edildi. Yine 200 0 C tavlanmis diyot icin oda sicakliginda idealite faktoru ve engel yuksekligi sirasiyla 1,11 ve 0,73 eV olarak hesaplanmistir. Buna gore tavlama neticesinde diyot tavlama sicakligina bagli olarak daha kararli hale geldigi soylenebilir. Bu durum, metal yariiletken arayuzeyindeki istenmeyen fazlarin tavlama sicakligina bagli olarak azaldiginin veya buyuk olcude yok oldugunun bir kanitidir. Au/n-Si/Al Schottky diyotlarin oda sicakliginda tavlanmadan once ve 200 0 C’de tavlandiktan sonra seri direnc ve engel yuksekligi degerleri Norde Fonksiyonlari kullanilarak hesaplandi.