Yazar "Demir, Gulcin Ersoz" seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim Yok
    Öğe
    DETERMINATION OF MAIN ELECTRICAL PARAMETERS OF Au-4H-n-SiC (MS) AND Au-Al2O3-4H-n-SiC (MIS) DEVICES
    (World Scientific Publ Co Pte Ltd, 2021) Demir, Gulcin Ersoz; Yucedag, Ibrahim
    In this study, Au-4H-n-SiC metal-semiconductor (MS) and Au-Al2O3-4H-n-SiC metal-insulator-semiconductor (MIS) devices were fabricated to examine the effects on the performance of electronic devices of interfacial insulating materials. In order to determine the dielectric properties, capacitance/conductance-voltage (C/G-V) measurements were realized in a wide range of voltages (-3.0 V)-(11.0 V). Current-voltage (I-V) measurements to obtain the electric properties were realized at +/- 2:5V. Moreover, both the energy distributions of surface states (N-ss) and series resistance (R-s) were obtained from the C/G-V data. Obtained results provided that series resistance originating from interfacial layer (Al2O3) was more effective on the I-V and C/G-V characteristics which must be taken into account in the calculation of main electrical parameters. The rectification ratio (RR) and shunt resistance (R-sh) of the MIS device were almost 10(3) times greater than those of the MS structure. Using Al2O3 between Au and 4H-n-SiC also led to an increase in the value of barrier height (BH) and a decrease in the value of ideality factor (n). These results confirmed that Al2O3 layer leads to an increase in the performance of MS device with respect to low values of N-ss, reverse saturation current (I-0) and n and high values of RR, R-sh and BH.
  • Küçük Resim Yok
    Öğe
    Engineering the interface of Schottky diodes with a PVA:(CoFe2O4-rGO) nanocomposite for enhanced frequency response via admittance spectroscopy
    (World Scientific Publ Co Pte Ltd, 2026) Demir, Gulcin Ersoz; Yeriskin, Seckin Altindal; Yildiz, Kevser; Kalandaragh, Yashar Azizian
    This study examines the frequency- and voltage-dependent electrical parameters, interface trap densities (D-it) and relaxation times (tau) in Au/PVA:(CoFe2O4-rGO)/n-Si structures using three complementary admittance methods. CoFe2O4 nanoparticles, synthesized hydrothermally, were incorporated with reduced graphene oxide (rGO) into polyvinyl alcohol (PVA) matrices and spin-coated onto n-Si substrates to form interfacial layers. Capacitance-voltage (C-V) and conductance-voltage (G/ omega -V) measurements spanned - 2.0- + 3.0 V across 0.3 kHz-3 MHz. Pronounced frequency dispersion was observed: forward-bias capacitance at + 3.0 V fell from similar to 9 nF (0.3 kHz) to similar to 2.5 nF (3 MHz), while the normalized conductance peaked near 0.8-1.0 V at all frequencies, with trap saturation above similar to 0.75 V. Hill-Coleman analysis revealed D i t values that decline quasi-exponentially from similar to 1 . 3 & times; 10 (14) eV( - 1) cm (- 2 )at low frequencies to similar to 1 . 0 & times; 10 (13) eV (- 1) cm( - 2 )at high frequencies. Parallel-conductance extraction revealed tau spanning three orders of magnitude, from similar to 120 mu s at 0.20 V to similar to 0.08 mu s at 1.60 V, with the normalized conductance saturating above similar to 0.75 V, consistent with strong field-induced acceleration of trap dynamics and near-complete filling of accessible trap levels under moderate forward bias. This behavior arises because the AC period shortens relative to tau : once the period falls below the trap response time, slower states cease contributing to the measured admittance. The apparent donor concentration decreased from similar to 2 . 1 5 & times; 10(17) cm(- 3) to similar to 7 . 7 & times; 10 (15) cm (- 3) over the same frequency range, while the depletion width expanded from 6.6 mu m to 39.9 mu m, and the peak electric field diminished from similar to 2 . 1 7 & times; 10(5) V/cm to similar to 4 . 7 5 & times; 10(4 )V/cm over the same frequency. Unlike conventional low-dielectric interlayers that cannot fully suppress interface states or reduce series resistance, the high-dielectric PVA:(CoFe2O4-rGO) nanocomposite studied here offers a broader operating window by neutralizing a substantial fraction of N s s while regulating charge transport mechanisms. To our knowledge, this is the first frequency-resolved, multi-method mapping of D-it and tau distributions in such a system, offering practical guidance for engineering nanocomposite interlayers with tailored trap spectra.
  • Küçük Resim Yok
    Öğe
    Fabrication of photonic sensor-based Al/(Ag:ZnO:rGO-PVA)/n-Si/Al structures and investigation of their charge transport mechanisms in wide voltage and illumination ranges
    (Elsevier Science Sa, 2026) Yeriskin, Seckin Altindal; Demir, Gulcin Ersoz
    In this study, photonic sensor-based Al/(AgZnO:rGO(5%)-PVA)/n-Si/Al structures were fabricated and characterized through comprehensive electrical/optoelectronic measurements. Current-voltage (I-V) characteristics were investigated in dark and under various illumination-intensities (20-100 mW/cm(2)), while capacitance/conductance-voltage (C-V, G/omega-V) measurements were performed at 1 MHz and spanning -2.5 V to + 4.5 V. The fabricated-device exhibited pronounced rectifying-ratio (RR=I-for./I-rev.) exceeding four-orders of magnitude. Key electrical-parameters extracted included ideality-factors of 6.573-7.983 (Region-I) and 13.671-15.451 (Region-II), barrier heights (BHs) of 0.676-0.646 eV (I-V) and 1.124 eV (C-V), doping donor-concentration of 5.08 & times; 10(17)cm(-3), and depletion-width (W-d) of 159 nm. Barrier-height decreased linearly with light (Phi(B0)=-2.95 & times;10(-4)P+0.675 eV), yielding an illumination-coefficient (-2.95 & times;10(-4)eV/(mW/cm(2))) approaching silicon's temperature-coefficient (-4.73 & times;10(-4)eV/K). Photovoltaic parameters under 100 mW/cm(2) included a fill factor (FF) of 58% and an efficiency (tau) of 1.11%. Photocurrent exhibited supralinear power-law dependence (exponents 1.3054 at -2V, 1.2032 at 0 V), indicating interface-trap emptying and space-charge-region generation-recombination (GR) mechanisms. Series-resistance (R-s) decreased from 12.40 Omega to 10.61 Omega under illumination, while shunt-resistance (R-sh) dropped from 96.2k Omega to 0.491k Omega. Interface-state densities (N-ss) of 10(12)-10(13) eV(-1)cm(-2) accounted for elevated ideality factors. The composite interlayer, combining reduced graphene oxide (rGO) percolation pathways with AgZnO plasmonic enhancement, demonstrated a substantial bidirectional photo-response, establishing this architecture as promising for PS applications that are superior to conventional metal-insulator-semiconductor (MIS) structures.
  • Küçük Resim
    Öğe
    Investigation of the variation of dielectric properties by applying frequency and voltage to Al/(CdS-PVA)/p-Si structures
    (Elsevier, 2021) Azizian-Kalandaragh, Yashar; Yucedag, Ibrahim; Demir, Gulcin Ersoz; Altindal, Semsettin
    In this study, the effect of frequency and voltage on the dielectric properties of Al/(CdS-PVA)/p-Si structures prepared using cadmium sulfide (CdS)-polivinyl alcohol (PVA) interface material was investigated. For this purpose, real and imaginary permittivity (epsilon' and epsilon ''), dissipation factor (tan delta), ac electrical conduction mechanism (sigma(ac)), real and imaginary part of electric modulus (M' and M) were obtained by using capacitance-conductance (C-G/omega) measurements at frequency between 5kHz - 5MHz and at voltage between (-1V) - (+1V). All parameters were found to depend considerably on the frequency and voltage. epsilon' and epsilon '' reach higher values at low frequencies due to surface states (N-ss) which can easily monitor ac signal, dipolar polarization and interfacial polarization. Short-range mobility of charge carriers caused the increase of both electrical modulus and sigma(ac) with increasing frequency. Moreover, M '' exhibited a peak behavior which shifts to higher frequency with increasing voltage. Peak behavior could be ascribed to both decrease in polarization and surface states. (C) 2020 Elsevier B.V. All rights reserved.