Search query: screening of hot electrons

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author_names: Yanan Dai

Mark E Ziffer

Xiaoyang Zhu
title: Screening of hot electrons in the ferroelectric semiconductor In2Se3
year: 2020

abstract: A theoretical model is proposed to calculate the energy loss rates of hot electrons in semiconductors in high magnetic fields at low temperatures. The energy loss due to the acoustic phonon scattering via deformation potential and piezoelectric coupling is considered for lowest Landau level occupancy, i.e. the extreme quantum limit. The model includes the effect of the modified free carrier screening due to Landau quantisation, on the acoustic phonon scattering, assumed to be the dominant loss mechanisms. The band nonparabolicity, the non equipartition of acoustic phonons, and the Landau level broadening due to electron impurity interactions are also included. The model is used to interpret the experimental results obtained from the specific heat measurements in n Hg0.8Cd0.2Te at 1.5 K. The theoretical values of the energy loss rate are found to be larger compared to the experimental values. The inclusion of quantum effects on the free carrier screening overestimates the theoretical energy loss rates. Es wird ein theoretisches Modell fur die Berechnung der Energieverlustraten heiser Elektronen in Halbleitern in hohen Magnetfeldern bei tiefen Temperaturen vorgeschlagen. Der Energieverlust durch Streuung akustischer Phononen uber Deformationspotential und piezoelektrischer Kopplung wird fur Besetzung des tiefsten Landauniveaus, d. h. fur den extremen Quantengrenzfall betrachtet. Das Modell schliest den Einflus der modifizierten Abschirmung freier Trager infolge der Landauquantisierung auf die als dominierender Verlustmechanismus angenommene Streuung akustischer Phononen ein. Die Nichtparabolizitat der Bander, die Nichtgleichverteilung der akustischen Phononen sowie die Landauniveauverbreitung infolge von Elektronen Storstellen Wechselwirkung werden ebenfalls einbezogen. Das Modell wird benutzt, um die aus den Messungen der spezifischen Warme an n Hg0,8Cd0,2Te bei 1,5 K erhaltenen experimentellen Ergebnisse zu interpretieren. Es wird gefunden, das die theoretischen Werte der Energieverlustrate im Vergleich zu den experimentellen Werten groser sind. Die Einbeziehung von Quanteneffekten auf die Abschirmung freier Trager uberschatzt die theoretischen Energieverlustraten.
author_names: Saumitra Bhowmik

Chandan Kumar Sarkar

K C Santra
title: The Effect of Quantum Screening on the Energy Loss Rates of Hot Electrons in n Hg0.8Cd0.2Te in the Extreme Quantum Limit at Low Temperatures
year: 1990

abstract: Energy relaxation of the hot electrons in Si doped bulk GaN is studied theoretically, taking into account non equilibrium polar optical phonons, electron degeneracy, and screening from the mobile electrons. The electron power dissipation and energy relaxation time are calculated as functions of the electron temperature Te, the hot phonon effect (HPE) is examined by varying the optical phonon lifetime values, and the results are compared with previous calculations for typical GaN based heterostructures. Particular attention is paid to the distinct temperature Te dependences of the power loss and the energy relaxation time tE at the low and high electron temperatures. At low electron temperatures (Te 1500 K) the power loss increases slowly with Te due to the decrease in phonon generation rate, and the
author_names: J -Z Zhang
title: Energy relaxation of hot electrons in Si doped GaN
year: 2014

abstract: The average energy loss rate (AELR, in an ensemble sense) of hot electrons via interactions with quasi equilibrium electron only and electron hole plasmas in bulk GaAs is calculated exactly, within the random phase approximation (RPA) Results are presented for plasma densities ranging from 4 X 1015 cm 3 to 1 X 1019 cm 3, and for temperatures ranging from 100 K to 300 K. Comparisons are made with simpler, static screening and plasmon pole approximations. Using the full RPA result, a critical plasma density is obtained beyond which the AELR decreases. A quantitative analysis of this behavior shows that it is due to both the Pauli exclusion principle, and to a blocking mechanism that occurs when plasmon emission processes become kinematically forbidden.
author_names: Jeff F Young

Paul J Kelly
title: Coulomb scattering of hot electrons with electron hole plasmas in GaAs: quantitative effects of dynamic screening (Invited Paper)
venue: Other Conferences
year: 1992

abstract: The net energy loss rate of a hot electron in GaAs due to Coulomb mediated interactions with a quasi thermal electron hole plasma is calculated for a range of plasma densities, temperatures and initial hot electron energies. The energy loss rates obtained using a fully dynamic treatment (within the random phase approximation) of the screening are significantly larger than those estimated using the static screening approximation. Furthermore, a substantial portion of the hot electron's energy can be transferred to the plasma via the hole system when dynamic screening and intervalence band processes are included.
author_names: Jeff F Young

Paul J Kelly

Norm L Henry
title: Quantitative evaluation of the energy loss rate of hot electrons to cool electron hole plasmas including dynamic screening and intervalence band processes
year: 1992

abstract: In this paper we present theoretical calculations of the angle and mode dependence of the phonon emission by hot two dimensional electrons in gallium arsenide. We compare them with experimental results of heat pulse studies of the acoustic phonon emission in \mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\mathrm{A}\mathrm{l}}_{x}\mathrm{Ga}}_{1\ensuremath{ }x}\mathrm{As} heterojunctions and GaAs quantum wells. It is shown that the ratio of the strengths of the longitudinal and transverse acoustic modes is correctly predicted only by a theoretical model that properly includes the effects of acoustic anisotropy on the electron phonon matrix elements, screening, and the form of the confining potential. As a result of this work, we are finally able to account for why longitudinal phonon emission from a heterojunction is not seen in heat pulse experiments despite the fact that earlier theories predicted that it should be the dominant mode.
author_names: Dietmar Lehmann

Anthony J Kent

Cz Jasiukiewicz

Andrew J Cross

P Hawker

Mohamed Henini
title: Effects of acoustic anisotropy and screening on the energy relaxation of hot electrons in heterojunctions and quantum wells
year: 2002

abstract: Using the dielectric continuum model, hot electron power dissipation and energy relaxation times are calculated for a typical lattice matched AlInN/AlN/GaN heterostructure, including effects of hot phonons and screening from the mobile electrons. The calculated power dissipation and energy relaxation times are very close to the experimental data.
author_names: Ji-sen Zhang

Angela Dyson

B K Ridley
title: Energy relaxation of hot electrons in lattice matched AlInN/AlN/GaN heterostructures
year: 2013

abstract: The dynamics of nonthermal excitations of electrons and holes in solids determines many of their key properties of fundamental and practical importance. Such excitations and the accompanying response of the system are conveniently studied by the spectroscopies in which their evolution constitutes elementary stages of the measurement. Here we specifically consider the effects of ultrafast screening on hot electron and hole propagation in intermediate and emergent states of electron spectroscopies. We discuss how these phenomena affect and manifest themselves in the orbital and band structure of solids revealed by one photon, multiphoton, and inverse photoemission experiments.
author_names: Branko Gumhalter
title: Ultrafast Dynamics of Hot Electrons and Holes in Solids: Elementary Stages in the Spectroscopies of Surface Electronic Structure
year: 2013

abstract: Significance Two dimensional electron gases are an essential building block of today's technology and attract broad interest in the context of material science or nanoengineering. Their widespread applications in many strategical sectors call for a direct visualization of hot electrons relaxation in an accumulation layer. In this work, we make use of time resolved photoelectron spectroscopy to acquire snapshots of the electronic distribution after a strong and impulsive drive. We identified and quantified the remote coupling of the confined electrons to phonon modes of the adjacent polar material. The far reaching outcomes provide insights on the screening of electron phonon coupling in constrained dimensions and will be of high relevance for the development of aggressively downscaled circuits. Two dimensional electron gases (2DEGs) are at the base of current nanoelectronics because of their exceptional mobilities. Often the accumulation layer forms at polar interfaces with longitudinal optical (LO) modes. In most cases, the many body screening of the quasi 2DEGs dramatically reduces the Frohlich scattering strength. Despite the effectiveness of such a process, it has been recurrently proposed that a remote coupling with LO phonons persists even at high carrier concentration. We address this issue by perturbing electrons in an accumulation layer via an ultrafast laser pulse and monitoring their relaxation via time and momentum resolved spectroscopy. The cooling rate of excited carriers is monitored at doping level spanning from the semiconducting to the metallic limit. We observe that screening of LO phonons is not as efficient as it would be in a strictly 2D system. The large discrepancy is due to the remote coupling of confined states with the bulk. Our data indicate that the effect of such a remote coupling can be mimicked by a 3D Frohlich interaction with Thomas Fermi screening. These conclusions are very general and should apply to field effect transistors (FET) with high k dielectric gates, van der Waals heterostructures, and metallic interfaces between insulating oxides.
author_names: Zhesheng Chen

Jelena Sjakste

Jingwei Dong

Amina Taleb-Ibrahimi

J P Rueff

Abhay Shukla

Jacques Peretti

Evangelos Papalazarou

Marino Marsi

Luca Perfetti
title: Ultrafast dynamics of hot carriers in a quasi two dimensional electron gas on InSe
venue: Proceedings of the National Academy of Sciences
year: 2020

abstract: Understanding and controlling properties of plasmon induced hot carriers is a key step toward next generation photovoltaic and photocatalytic devices. Here, we uncover a route to engineering hot carrier generation rates of silver nanoparticles by designed embedding in dielectric host materials. Extending our recently established quantum mechanical approach to describe the decay of quantized plasmons into hot carriers we capture both external screening by the nanoparticle environment and internal screening by silver d electrons through an effective electron electron interaction. We find that hot carrier generation can be maximized by engineering the dielectric host material such that the energy of the localized surface plasmon coincides with the highest value of the nanoparticle joint density of states. This allows us to uncover a path to control the energy of the carriers and the amount produced, for example, a large number of relatively low energy carriers are obtained by embedding in strongly screening environments.
author_names: Lara Roman Castellanos

Ortwin Hess

Johannes Lischner
title: Dielectric Engineering of Hot Carrier Generation by Quantized Plasmons in Embedded Silver Nanoparticles
venue: The journal of physical chemistry. C, Nanomaterials and interfaces
year: 2021