Browsing by Author "Uslu, H."

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Electrical characterization of MS and MIS structures on AlGaN/AlN/GaN heterostructures
    (ELSEVIER, 2010) Arslan, E.; Bütün, S.; Şafak, Y.; Uslu, H.; Tascioglu I.; Altindal, S.; Özbay, Ekmel
    The forward and reverse bias I-V, C-V, and G/ω-V characteristics of (Ni/Au) Schottky barrier diodes (SBDs) on the Al 0.22Ga 0.78N/AlN/GaN high-electron-mobility-transistor (HEMTs) without and with SiN x insulator layer were measured at room temperature in order to investigate the effects of the insulator layer (SiN x) on the main electrical parameters such as the ideality factor (n), zero-bias barrier height ( B0), series resistance (R s), interface-state density (N ss). The energy density distribution profiles of the N ss were obtained from the forward bias I-V characteristics by taking into account the voltage dependence of the effective barrier height ( e) and ideality factor (n V) of devices. In addition, the N ss as a function of E c-E ss was determined from the low-high frequency capacitance methods. It was found that the values of N ss and R s in SBD HEMTs decreases with increasing insulator layer thickness.
  • Thumbnail Image
    ItemOpen Access
    Frequency and temperature dependence of the dielectric and AC electrical conductivity in (Ni/Au)/AlGaN/AlN/GaN heterostructures
    (Elsevier, 2010) Arslan, E.; Şafak, Y.; Taşçioğlu, I.; Uslu, H.; Özbay, Ekmel
    The dielectric properties and AC electrical conductivity (σ ac)of the (Ni/Au)/Al 0.22Ga 0.78N/AlN/GaN heterostructures, with and without the SiNx passivation, have been investigated by capacitance-voltage and conductance-voltage measurements in the wide frequency (5kHz-5 MHz) and temperature (80-400 K) range. The experimental values of the dielectric constant (ε'), dielectric loss (ε' '), loss tangent (tand), σ ac and the real and imaginary part of the electric modulus (M' and M' ') were found to be a strong function of frequency and temperature. A decrease in the values of ε' and ε' ' was observed, in which they both showed an increase in frequency and temperature. The values of M' and M' ' increase with increasing frequency and temperature. The σ ac increases with increasing frequency, while it decreases with increasing temperature. It can be concluded, therefore, that the interfacial polarization can occur more easily at low frequencies and temperatures with the number of interface states density located at the metal/semiconductor interface. It contributes to the e' and σ ac. © 2009 Elsevier B.V. All rights reserved.
  • Thumbnail Image
    ItemOpen Access
    Frequency dependent electrical characteristics of (Ni/Au)/AlGaN/AlN/GaN heterostructures
    (Optoelectronica,National Institute of Research and Development for Optoelectronics, 2010) Taşçioǧlu, I.; Uslu, H.; Şafak, Y.; Özbay, Ekmel
    The main electrical parameters such as ideality factor (n), zero bias barrier height (Bo), series resistances (R s), depletion layer width (W D) and interface state densities (N SS) of (Ni/Au)/AlGaN/AlN/GaN heterostructures have been extracted from the current-voltage (I-V) at room temperature, and frequency dependent capacitance voltage (C-V) and conductance-voltage (G/w-V) measurements. The high value of n and R s were attributed to the existence of an interfacial layer (IL) and particular distribution of N ss. The density distrubition profile of N ss was obtained from both forward bias I-V data and low-high frequency (C LF-C HF) measurement methods. In addition, the voltage dependent R s profile obtained both I-V and admittance measurements are in good agreement. As a result, the existence of an IL, R s and N ss lead to deviation from the ideal case of these heterostructures.