On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current–voltage (I–V) and admittance spectroscopy methods

Cataloged from PDF version of article.In order to explain the experimental effect of interface states (N-ss) and series resistance (R-s) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/omega-V) characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/omega-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (-5 V)-(+5 V), respectively. The voltage dependent R-s profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (sigma(ac)) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C-m) and conductance (G(m)/omega) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of N-ss and R-s is confirmed to have significant effect on non-ideal I-V. C-V and G/omega-V characteristics of (Ni/Au)/Al0.22Ga038N/AlN/GaN heterostructures. (C) 2011 Elsevier Ltd. All rights reserved

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

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. © 2010 Taylor & Francis

WITHDRAWN: Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofibers capacitors

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Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

AbstractIn this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε′, ε′, tanδ, electric modulus (M′ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε′, ε′, tanδ, M′, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε′, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε′ and ε″ values at low frequencies may be attributed to the Maxwell–Wagner and space charge polarization. The high values of ε′ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M′ and M″ reach a maximum constant value corresponding to M∞≈1/ε∞ due to the relaxation process at high frequencies, but both the values of M′ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε′, ε″, tanδ, M′, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization

Growth parameter investigation of Al0.25Ga0.75N/GaN/ AlN heterostructures with Hall effect measurements

Hall effect measurements on unintentionally doped Al0.25Ga 0.75N/GaN/AlN heterostructures grown by metal organic chemical vapor deposition (MOCVD) were carried out as a function of temperature (20-300 K) and magnetic field (0-1.4 T). Magnetic-field-dependent Hall data are analyzed using the quantitative mobility spectrum analysis (QMSA) technique. The QMSA technique successfully separated electrons in the 2D electron gas (2DEG) at the Al 0.25Ga0.75N/GaN interface from other 2D and 3D conduction mechanisms of the samples. 2DEG mobilities, carrier densities and conductivities of the investigated samples are compared at room temperature and low temperature (20 K). For a detailed investigation of the 2DEG-related growth parameters, the scattering analyses of the extracted 2DEG were carried out for all of the samples. Using the results of the scattering analyses, the relation between the growth and scattering parameters was investigated. Increments in the interface roughness (IFR) are reported with the increased GaN buffer growth temperatures. In addition, a linear relation between the deformation potential and interface roughness (IFR) scattering is pointed out for the investigated samples, which may lead to a better understanding of the mechanism of IFR scattering. © 2008 IOP Publishing Ltd

Growth parameter investigation of Al(0.25)Ga(0.75)N/GaN/AlN heterostructures with Hall effect measurements

WOS: 000258875200008Hall effect measurements on unintentionally doped Al(0.25)Ga(0.75)N/GaN/AlN heterostructures grown by metal organic chemical vapor deposition (MOCVD) were carried out as a function of temperature (20-300 K) and magnetic field (0-1.4 T). Magnetic-field-dependent Hall data are analyzed using the quantitative mobility spectrum analysis (QMSA) technique. The QMSA technique successfully separated electrons in the 2D electron gas (2DEG) at the Al(0.25)Ga(0.75)N/GaN interface from other 2D and 3D conduction mechanisms of the samples. 2DEG mobilities, carrier densities and conductivities of the investigated samples are compared at room temperature and low temperature (20 K). For a detailed investigation of the 2DEG-related growth parameters, the scattering analyses of the extracted 2DEG were carried out for all of the samples. Using the results of the scattering analyses, the relation between the growth and scattering parameters was investigated. Increments in the interface roughness (IFR) are reported with the increased GaN buffer growth temperatures. In addition, a linear relation between the deformation potential and interface roughness (IFR) scattering is pointed out for the investigated samples, which may lead to a better understanding of the mechanism of IFR scattering.State of Planning Organization of TurkeyTurkiye Cumhuriyeti Kalkinma Bakanligi [2001K120590]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [104E090, 105E066, 105A005]; Turkish Academy of SciencesTurkish Academy of SciencesThis work is supported by the State of Planning Organization of Turkey under Grant no. 2001K120590 and by TUBITAK under Project nos. 104E090, 105E066 and 105A005. One of the authors (Ekmel Ozbay) acknowledges partial support from the Turkish Academy of Sciences