Transport parameters of 2D systems derived from microwave transmission experiments

This paper reports on low temperature microwave transmission experiments which are performed in high magnetic fields on two-dimensional electron gas (2DEG) systems of heterostructure quantum wells. The main transport parameters of the 2DEG, namely, the electron concentration n(s) the mobility my, and the effective mass m*, are evaluated from the transmitted microwave power. We use two alternative configurations to couple the microwaves into the 2DEG: first the sample fills a rectangular waveguide where the microwaves (26.5-40 GHz) propagate parallel to the magnetic field B (Faraday configuration), second, the microwaves (2-18 GHz) are guided by a coplanar structure mounted on the top of the sample which leads to a Voigt configuration. For both arrangements the microwave power transmitted greatly depends on B according to the respective correlation between microwave transmission and the high frequency conductivity tensor sigma of the 2DEG. Well-pronounced Shubnikov-de Haas oscillations are observed. We compare the discussed methods with respect to experimental feasibility, reproducibility, and data extraction.