Abstract

We elaborate the effects of carrier heating on the mobility characteristics of MOSFET inversion layers in the range of interest for devices of practical technological import (transverse fields ET ≈ 0.1 to 1 MV/cm), insofar as they are underpinned and governed by energy and momentum conservation principles. Carrier heating relatively to their surrounding lattice begins when the transverse (gate) electric field ET approaches the saturation field of carriers' thermal velocity, a material property. Additional energy imparted to carriers by yet higher fields causes their mean velocity, hence their longitudinal velocity component, to fall as required by momentum conservation. Whereas energy is converted predominantly from potential to kinetic form at relatively low fields where the flow of carriers is quasi-laminar, potential energy is converted (lost) to thermal energy in the saturated velocity range. The degradation of mobility is thermally-mediated: it 'emerges' by virtue of nonlinear interactions between transverse field, saturation velocity, and carrier heating, and is constrained by overarching conservation laws. Our findings indicate that the rate of carrier heating is a function only of interface terrain 'roughness' amplitude and fundamental constants, hence that the influence of surface orientation is ancillary to the heating phenomenon. Our analytical results are surprisingly simple, intuitively appealing, and in uniform agreement with Takagi et al's extensive observations of long standing, when the latter are apprehended in light of the unifying percepts and order herein set forth. As such, they readily inform the modeling of silicon and silicon carbide integrated MOSFET technologies. 1 Which has ostensibly become all but synonymous with "universal" in the pertinent literature. " As levels of complexity mount, … new properties arise as results and interconnections emerging at each new level. A higher level cannot be fully explained by taking it apart into component elements and rendering their properties in the absence of these interactions." [1]