Browsing by Subject "Series resistance"

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    The effect of insulator layer thickness on the main electrical parameters in (Ni/Au)/AlxGa1-xN/AIN/GaN heterostructures
    (Wiley, 2010) Altindal, S.; Şafak, Y.; Taşçloǧlu I.; Özbay, Ekmel
    (Ni/Au)Alx Ga1-x N/AlN/GaN(x = 0.22) heterostructures with and without a passivation layer of the SiNx were fabricated in order to see the effect of the insulator layer on the main electrical parameters such as zero-bias barrier height (BH) (φBO), ideality factor (n), series resistance (Rs) of the structure, and the interface state density (Nss). Some of these parameters were determined from both I-V and admittance (C-V and G/ω-V) measurements at room temperature and at 1 MHz and were compared. The experimental results show that the value of N ss in a Schottky contact without passivation is nearly 1 order of magnitude larger than that in a Schottky contact with SiNx passivation layers. Also, the values of Rs increase with the increasing thickness of the passivation layer. In the forward bias region, the negative values of capacitance are an attractive result of this study. This negative capacitance disappears in presence of the passivation layer. Copyright © 2010 John Wiley & Sons, Ltd.
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    ItemOpen Access
    On the interface states and series resistance profiles of (Ni/Au)-Al 0.22Ga0.78N/AlN/GaN heterostructures before and after 60Co (γ-ray) irradiation
    (Taylor and Francis, 2010-06-09) Demirezen, S.; Altndal, S.; Özçelik, S.; Özbay, Ekmel
    The values of interface states (NSS) and series resistance (RS) of (Ni/Au)-Al0.22Ga0.78N/AlN/GaN heterostructures were obtained from admittance and current-voltage measurements before and after 250kGy 60Co irradiation. The analyses of these data indicate that the values of capacitance and conductance decrease, as the R S increases with increasing dose rate due to the generation of N SS. The increase in RS with increasing dose rate was attributed to two main models. According to the first model, it has been attributed to a direct decrease in the donor concentration in semiconductor material as a result of the elimination of shallow donor states. According to the second model, it is a result of irradiation because of the formation of deep acceptor centers in the semiconductor bulk, and electrons from the shallow donor centers are captured by these acceptors.
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    ItemOpen Access
    The profile of temperature and voltage dependent series resistance and the interface states in (Ni/Au)/Al0.3Ga0.7N/AlN/GaN heterostructures
    (Elsevier BV, 2008-11) Tekeli, Z.; Altındal, Ş.; Çakmak, M.; Özçelik, S.; Özbay, Ekmel
    The temperature dependence of capacitance–voltage (C–V) and the conductance–voltage (G/w–V) characteristics of (Ni/Au)/Al0.3Ga0.7N/AlN/GaN heterostructures were investigated by considering the effect of series resistance (Rs) and interface states Nss in a wide temperature range (79–395 K). Our experimental results show that both Rs and Nss were found to be strongly functional with temperature and bias voltage. Therefore, they affect the (C–V) and (G/w–V) characteristics. The values of capacitance give two peaks at high temperatures, and a crossing at a certain bias voltage point (∼3.5 V). The first capacitance peaks are located in the forward bias region (∼0.1 V) at a low temperature. However, from 295 K the second capacitance peaks appear and then shift towards the reverse bias region that is located at ∼−4.5 V with increasing temperature. Such behavior, as demonstrated by these anomalous peaks, can be attributed to the thermal restructuring and reordering of the interface states. The capacitance (Cm) and conductance (G/w–V) values that were measured under both reverse and forward bias were corrected for the effect of series resistance in order to obtain the real diode capacitance and conductance. The density of Nss, depending on the temperature, was determined from the (C–V) and (G/w–V) data using the Hill–Coleman Method.
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    Ta/Si Schottky diodes fabricated by magnetron sputtering technique
    (2010) Ocak, Y.S.; Genisel, M.F.; Kiliçoǧlu, T.
    Electrical properties of Ta/n-Si and Ta/p-Si Schottky barrier diodes obtained by sputtering of tantalum (Ta) metal on semiconductors have been investigated. The characteristic parameters of these contacts like barrier height, ideality factor and series resistance have been calculated using current voltage (I-V) measurements. It has seen that the diodes have ideality factors more than unity and the sum of their barrier heights is 1.21 eV which is higher than the band gap of the silicon (1.12 eV). The results have been attributed the effects of inhomogeneities at the interface of the devices and native oxide layer. In addition, the barrier height values determined using capacitance-voltage (C-V) measurements have been compared the ones obtained from I-V measurements. It has seen that the interface states have strong effects on electrical properties of the diodes such as C-V and Rs-V measurements. © 2010 Elsevier Ltd. All rights reserved.
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    Temperature-dependent profile of the surface states and series resistance in (Ni/Au)/AIGaN/AIN/GaN heterostructures
    (Wiley, 2010-03-28) Taşçıoğlu, I.; Aydemir, U.; Şafak, Y.; Özbay, Ekmel
    The profile of the interface state densities(N ss) and series resistances (R s) effect on capacitance-voltage (C-V) and conductancevoltage (G/ω-V) of (Ni/Au)/Al xGa 1-xN/AIN/ GaN heterostructures as a function of the temperature have been investigated at 1 MHz. The admittance method allows us to obtain the parameters characterizing the metal/semiconductor interface phenomena as well as the bulk phenomena. The method revealed that the density of interface states decreases with increasing temperature. Such a behavior of N ss can be attributed to reordering and restructure of surface charges. The value of series R s decreases with decreasing temperature. This behavior of R s is in obvious disagreement with that reported in the literature. It is found that the N ss and R s of the structure are important parameters that strongly influence the electrical parameters of (Ni/Au)/Al xGa 1-XN/AlN/GaN(x = 0.22) heterostructures. In addition, in the forward bias region a negative contribution to the capacitance C has been observed, that decreases with the increasing temperature.