The investigation of temperature and radiation dependent electrical and dielectric characteristics of Al/HfO2/p-Si (MIS) structure


Thesis Type: Doctorate

Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2013

Student: SEDA BENGİ

Supervisor: MEHMET MAHİR BÜLBÜL

Abstract:

The forward and reverse bias current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/w-V) characteristics of Al/HfO2/p-Si Metal-Insulator-Semiconductor (MIS) structure have been investigated over the temperature range of 80-400 K. By using the thermionic emission (TE) theory, the zero-bias barrier height (B) and ideality factor (n) values for the device have been obtained as 0.28 eV and 3.88 at 80 K and 0.90 eV and 2.81 at 400 K, respectively. The conventional Richardson plot of the ln(Io/T2) versus q/kT has a linear region and the values of activation energy (Ea) and Richardson constant (A*) were obtained from this plot and especially the value of A* is much lower than the known theoretical value for p-type Si. Also, the series resistance values of the device were found to change from 888.76  at 80 K to 122.10  at 400 K at 5 V. In addition, the temperature dependence of the energy distribution of interface state density (Nss) profiles has been determined by taking into account the bias dependence of the effective barrier height (e) and n. The decrease of the values of Nss with increasing temperature has been attributed to the molecular restructuring and reordering at the oxide/semiconductor interface. The C-V and G/w-V characteristics confirm that the Nss and Rs of the diode are important parameters that strongly influence the electrical properties of MIS structure. It is found that in the presence of series resistance, the forward bias C-V plots exhibits a peak, and its position shifts towards lower voltages with increasing temperature. At the same time, the density of Nss, depending on the temperature, was determined from the C-V and G/w-V data using the Hill-Coleman Method. Also, the temperature dependence of dielectric properties at three different frequencies over the temperature range of 80-400 K was investigated. The electric modulus formalisms were employed to understand the relaxation mechanism of the Al/HfO2/p-Si structure. In addition, to see gamma-ray irradiation effect on electrical characteristics of Al/HfO2/p-Si structure, the sample was exposed to 60Co (-ray) source at 100 kGy. It was seen that the barrier height calculated from I-V characteristics decreased, while the ideality factor and series resistance values increased after the applied radiation. It was also seen that the carrier concentration, the capacitance and conductance of device decreased with radiation dose.