Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2010
Thesis Language: Turkish
Student: Selçuk DEMİREZEN
Supervisor: ŞEMSETTİN ALTINDAL
Open Archive Collection: AVESIS Open Access Collection
Abstract:The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/w-V) characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures were measured in the temperature range of 80-400 K. Calculated from I-V characteristics according to thermionic emission (TE) theory; while the zero bias barrier height (ΦBo) increases with increasing temperature, the ideality factor (n) values decreases with increasing temperature. The Richardson plot deviated from linearity under room temperatures. Such behavior is attributed to inhomogeneties of Schottky barrier by assuming a double Gaussian distribution. It has been concluded that the temperature dependence of the forward I-V characteristics of the (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures can be successfully explained on the basis of TE mechanism with double Gaussian distribution of the barrier heights. Also, the forward and reverse bias C-V and G/w-V characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures have been investigated by considering the effect of the series resistance (Rs) and surface states (Nss) over a wide temperature of 80-400 K, at 1 MHz. The C-V and G/w-V characteristics confirm that the Nss and Rs of the heterostructure are important parameters that strongly influence the electrical parameters. The high frequency (1 MHz) C and G/w values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real heterostructure capacitance. Also the electrical conductivity (σac) is found to decrease with increasing temperature. The activation energy values were obtained from Arrhenius plot for various applied forward bias voltages. Calculated values are almost independent from applied forward bias voltage.