Showing papers on "Carbon nanotube field-effect transistor published in 1964"

Hall measurements on silicon field effect transistor structures

Abstract: The primary purpose of the work reported in this paper was to determine whether surface trapping plays any significant role in altering the transconductance of metaloxide-silicon field-effect transistors. Fang and Triebwasser • have reported that the effective mobility of carriers in the surface region of these devices followed a modified Schrieffer formula\" for diffuse scattering. However, since the mobility values were derived from transconductance measurements, effects of surface trapping could not be directly measured. We have measured the Hall constant, and hence the surface free-charge density, over a large enough range of gate voltage to show that trapping does not play a significant role in the region of interest and that a modified Schrieffer expression does fit the experimental data. The theory of Hall measurements on surface layers has been discussed by many workers starting with Petritz.t\":\" In general, experiments'v''\":\" have tended to demonstrate a decrease in mobility as the surface charge density is increased, and thus to confirm the existence of the effects of diffuse scattering. Most of the uncertainty in the results of such experiments relates to the confinement of the measuring current to the carriers on the surface; for instance, if the current is divided between a surface inversion region and the bulk, the measured Hall signal represents a sort of averaging of effects produced by the properties of the two regions.':\" In the samples we have used this difficulty is avoided in large measure in the case of n-p-n devices by making contact to the inversion layer with diffused n-type contacts. The resulting p-n junctions isolate the contacts from the high resistivity p-type bulk so that the current is confined to the surface except when the gate voltage is such that there is no or little inversion. Thus it is the properties of the surface region itself that are studied .