Comparison between WKB and Wavelet Approach for Analytical Calculation of Tunneling Currents in Schottky Barrier Field-Effect Transistors

The tunneling current in Schottky barrier field-effect transistors (SBFETs) is calculated by two analytical approaches. The Wentzels-Kramer-Brillouin (WKB) approximation and a method based on the wavelet transform are verified in comparison to numerical calculations using the non-equilibrium Green's function (NEGF). The results show that the WKB approximation overestimates the tunneling current for the onset of the tunneling current in the transfer characteristics of the device, especially at low temperatures. In contrast, the wavelet approach gives results which are in good agreement to the NEGF calculations. The conclusions are manifested by comparison to measurements performed on ultra-thin body and buried oxide SOI SBFETs at a temperature of 5.7 K. Therefore, the wavelet transform could be superior to the WKB approximation for the derivation of a compact device model.