The investigation of frequency dependent electrical characterization of Au/SrTiO3/n-Si (MFS) Schottky diodes

In this study, we investigated electrical characterization of RF sputtered SrTiO3 thin films deposited on n type Si substrate. Frequency dependent capacitance-voltage (C?V) and conductance-voltage (G/ ? ?V) characteristics of the Au/SrTiO3/n?Si structures have been investigated by considering the effect of series resistance (Rs) and interface states (Nss) in the frequency range of 5 kHz ? 2 MHz. The experimental C?V?f and G/ ? ?V?f characteristics of these structures show fairly large frequency dispersion, especially at low frequencies. The frequency and voltage dependent distribution profile of Rs and Nss were obtained by using admittance spectroscopy and Hill-Coleman methods, respectively. In addition, the energy density of Nss distribution profiles as a function Ec-Ess was extracted from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height (?e). The average value of interface states was found about 1013 eV-1cm-2. The C?V plots exhibit anomalous peaks due to the Nss and Rs effect. Also, the effect of Rs on the C-V and G/ ? -V characteristics is found appreciable at higher frequencies due to decreasing values of C and G/ ? with increasing frequency. Because of the presence of Nss, the device behavior is different from the ideal case of C-V and G/ ? -V characteristics. These Nss can easily follow the ac signal especially at low frequencies and yield an excess capacitance, which depends on their relaxation time and cause a bias shift of the C-V and G/ ? -V curves. Also we discussed the deep trap levels in Au/SrTiO3/n-Si structure using via Deep Level Transient Spectroscopy (DLTS) method. A deep trap level having 235 meV activation energy (Ea) was measured and given with capture cross section ( ? ) and trap concentration (Nt) parameters were in details.