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Effective mobility measurements have been made at 4.2 K on high performance high-k gated germanium p-type metal-oxide-semiconductor field effect transistors with a range of Ge/gate dielectric interface state densities. The mobility is successfully modelled by assuming surface roughness and interface charge scattering at the SiO 2 interlayer/Ge interface. The deduced interface charge density is approximately equal to the values obtained from the threshold voltage and subthreshold slope measurements on each device. A hydrogen anneal reduces both the interface state density and the surface root mean square roughness by 20%.

Silicon n-channel MOS transistors are a promising solution for sub-terahertz radiation detection. Their sensitivity is strongly related to the device construction. A type and thickness of the device substrate are key parameters affecting the responsivity, because the silicon substrate is a medium for the radiation propagation and the radiation energy loss, which degrades the detection efficiency. This work is aimed at analysis of the silicon substrate characteristics effect on operation of the MOSFETs as the terahertz radiation sensors. A manufacturing of the MOSFETs on three different substrate types including changing the substrate thickness is described in the paper. Next, the fabricated devices were exposed to THz radiation and their photoresponses were measured. It may be concluded that MOSFETs on silicon-on-insulator wafers with locally thinned substrates demonstrate the highest photoresponse. However, the experiments with the MOSFETs on high resisivity wafers give also promising results.

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