Simulation of Terahertz Frequency Sources. Polar-Optical Phonon Enhancement of Harmonic Generation in Schottky Diodes.

摘要

New algorithm has been developed for harmonic balance analysis. A robust simulation tool that combined this novel modified harmonic-balance circuit analysis technique with a two-valley temperature dependent hydrodynamic transport model device simulator is developed. We have demonstrated that polar- optical phonons dramatically affects the nonlinearity in capacitance of a material near its transverse polar optical vibration frequency. When a high frequency input signal is applied to a frequency multiplier device polar-optical phonons can enhance the non-linearities inherent in this device, enabling higher amplitude harmonic generation of the signal to yield better output power and output efficiency of the device. The incorporation of polar-optical phonon physics into the Schottky diode abrupt junction model was developed and applied in this work. Simulation of a GaAs-based Schottky diode multipliers was performed to show the dramatic enhancement of output efficiency in the vicinity of the polar-phonon frequency. In our simulation we have utilized a novel modified harmonic-balance circuit analysis technique which allows for the rapid determination of the matched embedding circuit and an optimized multiplier design. However, to practically utilize these novel nonlinear effects related to polar optical vibration within terahertz region, new materials were required with the Schottky diode barrier height to be of the same order as in GaAs, but with a lower transverse polar-phonon frequency. One of the candidates is Bi2S3, which has the transverse polar optical frequency on the order of 300GHz.