Hot Electron Transport and Current Sensing

Abstract

The effect of hot electrons on momentum scattering rates in a two-dimensional electron gas is critically examined. It is shown that with hot electrons it is possible to explore the temperature dependence of individual scattering mechanisms not easily probed under equilibrium conditions; both the Bloch-Gr¨uneisen (BG) phonon scattering phenomena and the reduction in impurity scattering are clearly observed. The theoretical calculations are consistent with the results obtained from hot electrons experiments. As a function of bias current, a resistance peak is formed in a 2DEG if the low temperature impurity limited mobilities ¹I(T = 0) is comparable to ¹ph(TBG) the phonon limited mobility at the critical BG temperature. In this case, as the bias current is increased, the electron temperature Te rises due to Joule heating and the rapid increase in phonon scattering can be detected before the effect of the reduction in impurity scattering sets in. If ¹I(T = 0) ≪ ¹ph(TBG), there is no peak in resistance because the impurity scattering dominates sufficiently and its reduction has a much Abstract iv stronger effect on the total resistance than the rise in phonon scattering. Furthermore, knowing the momentum relaxation rates allows us to analyze the possible interplay between electron-electron and electron-boundary scattering. The prediction that a Knudsen to Poiseuille (KP) transition similar to that of a classical gas can occur in electron flow [26] is examined for the case of a wire defined in a 2DEG. Concurrently, an appropriate current imaging technique to detect this transition is sought. A rigorous evaluation of magnetic force microscopy (MFM) as a possible candidate to detect Poiseuille electronic flow was conducted, and a method that exploits the mechanical resonance of the MFM cantilever was implemented to significantly improve its current sensitivity.