The origin of anomalous peak and negative capacitance in the forward bias C-V characteristics of Au/n-GaAs contacts at low temperatures (T?300 K)

Au/n-GaAs contacts were fabricated using n-GaAs wafer with high doping concentration and their electrical characteristics were investigated via admittance measurements at low temperatures (T?300 K) at 1MHz. The main electronic parameters such as barrier height, depletion region width, doping concentration, series resistance and Fermi energy were obtained from experimental data. All these parameters showed dependence on temperature since different conduction mechanisms may play role at a certain voltage and temperature range. The forward bias capacitance-voltage curve exhibited an anomalous peak and then capacitance took negative values for each temperature. Such negative capacitance behaviour can be explained by the loss of interface charges located at junction, the existence of surface states, series resistance and a native interlayer. The decrease in series resistance and increase in surface states with increasing temperature were attributed to the decrease in band gap of GaAs and restructuring and reordering of surface charges. © 2020 National Institute of Optoelectronics. All rights reserved.Gazi Ãœniversitesi: GU-BAP.05/2019-26This work was supported by Gazi University Scientific Research Project (GU-BAP.05/2019-26).2-s2.0-8509052230

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

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of epsilon', epsilon', tan delta, electric modulus (M' and M `') and sigma(ac) of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of epsilon', epsilon', tand, M', M `' and sigma(ac) of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of epsilon', epsilon `' and tand show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of sigma(ac) and the electric modulus increase with increasing frequency. The high dispersion in epsilon' and epsilon `' values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of epsilon' 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-infinity approximate to 1/epsilon(infinity) 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 N-ss and R-s of the capacitors. As a result, the change in the epsilon', epsilon `', tan delta, M', M `' and ac electric conductivity (sigma(ac)) 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. (C) 2016 The Authors. Published by Elsevier B.V