Cooling of electrons in a heavily doped silicon by quasiparticle tunneling using a superconductor–semiconductor–superconductor double-Schottky-junction structure is demonstrated at low temperatures. In this work, we use Al as the superconductor and thin silicon-on-insulator (SOI) film as the semiconductor. The electron–phonon coupling is measured for the SOI film and the low value of the coupling is shown to be the origin of the observed significant cooling effect.
We report on the effect of elastic intervalley scattering on the energy transport between electrons and phonons in many-valley semiconductors. We derive a general expression for the electron-phonon energy flow rate at the limit where elastic intervalley scattering dominates over diffusion. Electron heating experiments on heavily doped n-type Si samples with electron concentration in the range 3.5 − 16.0 × 10 25 m −3 are performed at sub-1 K temperatures. We find a good agreement between the theory and the experiment. Since the low temperature hot electron experiments by Roukes et al.[1], the energy transport between electrons and phonons has continued to be a topical subject. Recently, there has been significant experimental and theoretical interest in the electron-phonon (e-ph) energy relaxation in metals and semiconductors at low temperatures [2,3,4,5,6,7,8]. The understanding of thermal e-ph coupling is important for several low temperature devices such as microbolometers, calorimeters and on chip refrigerators [4,9]. This coupling plays also an important role in correct interpretation of low temperature experiments [5] and the e-ph energy relaxation rate gives direct information about phonon mediated electron dephasing [10].Interaction between electrons and phonons is strongly affected by the disorder of the electron system and, therefore, the problem is commonly divided into two special cases: pure and impure (or diffusive) limit of e-ph interaction. The cross-over between these two regions is defined as ql = 1 , where q is the phonon wavevector and l the electron mean free path. If the whole phonon system is to be considered then the phonon wavevector can be conveniently replaced by the thermal phonon wave vector q T = k B T / v, where T is the temperature of the lattice and v the sound velocity. Recent theory for single-valley semiconductors [8] predicts that the e-ph energy relaxation is strongly enhanced when the system enters from the pure limit (ql > 1) to the diffusive limit (ql < 1). The behavior is the opposite in comparison to metals where it is well known, since the pioneering work by A. B. Pippard [11], that the disorder of the electron system tends to suppress the e-ph energy relaxation (see also Ref.[2]). In semiconductors, due to small electron density, the e-ph interaction can be described by deformation potential coupling constants, which do not depend on the electronic variables, while in metals the coupling strongly depends on the electron momentum [12]. This fundamental difference eventually leads to disorder enhancement of the relaxation in the diffusive limit in single-valley semiconductors [8].In many-valley semiconductors the situation is further altered due to intervalley scattering, which is the topic of our work. Due to lack of screening the e-ph energy flow rate is strongly enhanced in many valley semiconductors in comparison to single valley ones at diffusive low temperature limit. We approach the e-ph energy transport problem by first considering the phonon energy attenuation r...
Articles you may be interested in Self-consistent calculations of inversion-layer mobility in highly doped silicon-on-insulator metal-oxide-semiconductor field-effect transistors J. Appl. Phys. 90, 866 (2001) Electron-phonon interaction and electronic thermal conductivity have been investigated in heavily doped silicon at subKelvin temperatures. The heat flow between electron and phonon systems is found to be proportional to T 6 . Utilization of a superconductor-semiconductor-superconductor thermometer enables a precise measurement of electron and substrate temperatures. The electronic thermal conductivity is consistent with the Wiedemann-Franz law.
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