Hot-electron transport in GaAs/Ga1-xAlxAs quantum-well structures

Magnetotransport Study on Iron Doped Novel 2D Nanoribbons via Electron – Acoustical Phonon Interactions

The electron transport parameters such as electron energy relaxation rate and phonon limited electron resistivity for iron (transition metal) doped 2D nanoribbons of armchair graphene nanoribbon (aGNR) and h-boron nitride nanoribbon (h-BNNR) have been calculated via hot electron acoustical phonon interactions on the basis of acoustical deformation potential (ADP) coupling mechanism. We have performed the investigation for the lower concentration ([Formula: see text]%) of iron doping under the influence of externally applied magnetic field at low temperature to room temperature regime. The hot electron acoustical phonon relaxation rates are observed with electric field and under constant applied magnetic field. The doping of iron increases the electron energy relaxation rate with respect to their pristine counter parts. Moreover, the pristine h-BNNR exhibits less electron energy relaxation rate with respect to pristine aGNR. Upon applying magnetic field on Fe doped armchair GNR as well as Fe-doped h-BNNR the electron energy relaxation rate reduces down to a considerable extent with respect to their pristine counterparts. Moreover, under the impact of magnetic field, the acoustical phonon restricted electrical resistivity of Fe-doped GNR is considerably low compared to pristine GNR.

Hot electron relaxation dynamics in semiconductors: assessing the strength of the electron-phonon coupling from the theoretical and experimental viewpoints

The rapid development of the computational methods based on density functional theory, on the one hand, and of time-, energy-, and momentum-resolved spectroscopy, on the other hand, allows today an unprecedently detailed insight into the processes governing hot-electron relaxation dynamics, and, in particular, into the role of the electron-phonon coupling. Instead of focusing on the development of a particular method, theoretical or experimental, this review aims to treat the progress in the understanding of the electron-phonon coupling which can be gained from both, on the basis of recently obtained results. We start by defining several regimes of hot electron relaxation via electron-phonon coupling, with respect to the electron excitation energy. We distinguish between energy and momentum relaxation of hot electrons, and summarize, for several semiconductors of the IV and III-V groups, the orders of magnitude of different relaxation times in different regimes, on the basis of known experimental and numerical data. Momentum relaxation times of hot electrons become very short around 1 eV above the bottom of the conduction band, and such ultrafast relaxation mechanisms are measurable only in the most recent pump-probe experiments. Then, we give an overview of the recent progress in the experimental techniques allowing to obtain detailed information on the hot-electron relaxation dynamics, with the main focus on time-, energy-, and momentum-resolved photoemission experiments. The particularities of the experimental approach developed by one of us, which allows to capture time-, energy-, and momentum-resolved hot-electron distributions, as well as to measure momentum relaxation times of the order of 10 fs, are discussed. We further discuss the main advances in the calculation of the electron-phonon scattering times from first principles over the past ten years, in semiconducting materials. Ab initio techniques and efficient interpolation methods provide the possibility to calculate electron-phonon scattering times with high precision at reasonable numerical cost. We highlight the methods of analysis of the obtained numerical results, which allow to give insight into the details of the electron-phonon scattering mechanisms. Finally, we discuss the concept of hot electron ensemble which has been proposed recently to describe the hot-electron relaxation dynamics in GaAs, the applicability of this concept to other materials, and its limitations. We also mention some open problems.

Capacitive-coupling-enhanced switching gain in an electron y-branch switch

We have fabricated electron Y-branch switches (YBS) on modulation doped GaAs/AlGaAs heterostructures. The Y branch consists of a one-dimensional source, which is split along the branching section into two one-dimensional drains. In addition to source drain voltages, external electric fields can be applied via gates along the branches. In the nonlinear transport regime sweeps of the side-gate voltages lead to a voltage difference between the drain reservoirs with gain. This switching gain increases superlinearly with the bias voltage applied between the source and the drains of the YBS. We explain the bias voltage enhanced switching by a capacitive coupling of the branches.