HgFET: A new characterization tool for SOI silicon film properties

Abstract

A new version of the pseudo-FET, called the HgFET, is described in which a combination of broad area Hg electrodes coupled with special surface treatment are used to overcome the limitations of point contacts. The device consists of a 20 mil diameter Hg mesa which act as the drain, completely surrounded by a ring of Hg acting as the source. This ring-dot configuration completely isolates the device from the rest of the wafer. Prior to contacting the Si surface with the Hg electrodes, the surface is treated with HF:H20 to remove any native or other oxide and `passivate' the surface, reducing the surface state density to a low level and introducing a layer of excess charge on the surface which influences the device characteristics but decays away in 30 to 60 minutes.