Bulk Loss Measurements of III-V Semiconductor Materials in a Microwave Cavity at Single Photon Powers and Millikelvin Temperatures*

Superconducting-semiconducting hybrid quantum systems look to integrate the success of superconducting qubits with the electronic tunability and half century of materials development in conventional semiconductor manufacturing. As the materials stack on the semiconductor side grows, there is an increasing need for characterizing the loss in these materials. We propose a method for extracting the bulk loss in semiconducting and dielectric samples loaded in the antinode of the TE101 mode of a superconducting rectangular cavity. Unlike in coplanar waveguide resonator studies where the fields are concentrated on the surfaces, the cavity field strongly probes the bulk of the material. This method lends itself to rapid measurements of materials in a controlled and repeatable microwave environment, opening up new studies that are incompatible with existing planar measurement techniques and measuring materials that are difficult to fabricate. We report bulk losses for Fe-doped, semi-insulating InP substrates loaded in a superconducting rectangular cavity. To validate our approach, we measured intrinsic Si with thermally grown SiO2 whose losses are well-documented [Appl.Phys.Lett. 92, 112903 (2008)].