Non-Contact Characterization of Two-Dimensional Electron Gas by Using Circularly Polarized TE<sub>11<i>n</i></sub> Modes

Two-dimensional electron gases (2DEGs) are essential not only for modern electronics but also for the advancement of next-generation communication technologies and quantum computing. Here, we report a non-contact method for characterizing material parameters of 2DEGs using circularly polarized TE11n modes. By developing an excitation method utilizing a circular patch antenna with an adjustable coupling hole, we enable the use of higher-order modes up to TE117, while minimizing the effects of cylindrical symmetry breaking. This method is demonstrated by measuring the magnetic field dependence of microwave conductivities in a GaAs/AlGaAs heterojunction at 300 K and 77 K. The electron mobility obtained by fitting to the Drude model is in good agreement with the results from standard Hall measurements. Additionally, the signature of cyclotron resonance is clearly observed at 77 K, and the effective electron mass is successfully estimated. The present method could accelerate fundamental research and device development using various 2DEGs.