Bias voltage effect on impedance, modulus and dielectric spectroscopies of HfO2-interlayered Si-based Schottky diodes at room temperature

Abstract

In this study, Al/HfO2/p-Si metal-insulator-semiconductor (MIS) Schottky diode was fabricated by atomic layer deposition (ALD) technique with an adjusted HfO2 interlayer thickness of 3.3 nm. Using (I, V), (Z, theta) and (C, G) experimental data sets, the electric and dielectric properties of the fabricated diode were investigated in 1 kHz-10 MHz frequency range at different applied bias voltages at room temperature through complex functions like impedance, modulus, conductivity and dielectric. From the DC current-voltage (I-V) measurements, the ideality factor and the barrier height of the diode were estimated at room temperature as 2.22 and 0.86 eV, respectively. AC measurement results demonstrated the presence of two different polarization mechanisms (interfacial and orientational) in the investigated frequency range. The results also clearly showed that three relaxation phenomena exist within the diode bulk structure, and that both relaxation and conduction mechanisms are activated by the applied bias voltage. One of the relaxations was the Warburg relaxation spotted in the low frequency region in two different forms (semi-infinite Warburg in impedance Nyquist plots and finite-space Warburg in dielectric Nyquist plots) and both were explained by the slow diffusion of Al3+, O2- and Hf4+ ions across the interface layer. Equivalent circuit impedance fit analysis showed that the fabricated diode has a good MIS structure due to the demonstrated high resistivity and low-leakage of the interfacial HfO2 layer. The big values of the dielectric loss tangent (8.03 at 500 kHz and +2 V) as compared to the dielectric constant (0.13 at 500 kHz and +2 V) at room temperature and the independence of dielectric constant on temperature suggests the appropriate usage of the fabricated diode in thermal heating applications. The estimated four major parameters (ideality factor, barrier height, dielectric constant and dielectric loss tangent) were compared with other literature results based on different growth parameters and tabulated in conclusion.