Monte Carlo simulation of GaAs schottky barrier diodes for THz applications

Abstract

Accurate models for GaAs Schottky barrier diodes are essential for implementing room-temperature mixers and frequency multipliers for use in the terahertz range. Increased electron temperatures by the Schottky contact and effects from intervalley scattering make traditional drift-diffusion methods unsuitable for simulating such devices. This work implements a Monte Carlo simulator based on a microscopic model for electron transport in GaAs. A three-valley (Γ,𝐿 and 𝑋) spherical non-parabolic band structure is assumed, and impurity, optical phonon and acoustic phonon scattering mechanisms are considered for the model. Homogeneous (bulk) transport properties of GaAs are simulated, showing good agreement with published values of mobility and diffusion coefficient versus field strengths, accurately predicting the critical field and saturation velocity for the carriers as they enter heavier valleys. The simulator is also used to simulate a number of Schottky barrier diodes fabricated at Chalmers University of Technology. The results show good agreement with the measured IV-characteristics, with the ideality factor being within 10% and saturation current within a factor of 3. The voltage-capacitance relationships agree well with the ideal diode model, the zero-voltage capacitance being within a few percent. The simulation shows an increased carrier temperature at the Schottky contact at higher currents, consistent with previous results, indicating an increased noise temperature at higher currents.