Compact Modeling of THZ Photomixer Made from GaN HEMT

The compact model of a terahertz photomixer made from the GaN HEMT is presented in this paper. In the proposed model, the photo beam is inputted to the absorption layer of HEMT through the ungated area using the excitation of plasma oscillation. Starting from the Euler equation and continuity equation, a response expression depicting the terahertz characteristics of that GaN HEMT photomixer with a cap region is derived. The response as a function of the signal frequency is analyzed and the dependence of resonant frequency and amplitude on different length of cap region, voltage, and physical parameters are demonstrated. The results may be useful for terahertz photomixer design and optimization.