Electron Velocity Overshoot, Electron Ballistic Transport, and Nonequilibrium Phonon Dynamics in Nanostructure Semiconductors

Chemistry and Properties of Nanocrystals of Different Shapes

“…Time-resolved nonlinear optical spectroscopy is a powerful tool for studying the energy structures and carrier dynamics in bulk and low-dimensional materials. ,− In nanoparticles, state-filling and Coulomb multiparticle interactions (the carrier-induced Stark effect) primarily cause resonant optical nonlinearities. , State-filling leads to bleaching of the interband optical transitions involving populated quantized states proportional to the sum of the electron and hole occupation numbers. If the linear absorption spectrum of nanocrystals is expressed as a sum of separate absorption bands corresponding to different quantized optical transitions, the induced absorption changes (Δα) can be expressed as where G i (ℏω − ℏω i ) is the unit-area absorption profile of the ℏω i transition, a i is the transition area (proportional to its oscillator strength), and and are occupation numbers of electron and hole states involved in the transition, respectively.…”

“…If the linear absorption spectrum of nanocrystals is expressed as a sum of separate absorption bands corresponding to different quantized optical transitions, the induced absorption changes (Δα) can be expressed as where G i (ℏω − ℏω i ) is the unit-area absorption profile of the ℏω i transition, a i is the transition area (proportional to its oscillator strength), and and are occupation numbers of electron and hole states involved in the transition, respectively. The occupation numbers can be found using the Fermi distribution function under thermal quasi-equilibrium after the intraband relaxation is finished. ,− After the electrons and holes are excited far from the equilibrium, both will return to the ground state after radiative and nonradiative relaxations, via carrier−carrier (electron−electron, hole−hole, and electron−hole), carrier−phonon, and phonon−phonon interactions. In the following, the carrier relaxation dynamics will be focused on the systems of nanoparticles, because detailed reviews regarding the carrier relaxation dynamics in quantum well systems have already been conducted …”

Non‐equilibrium carrier transport in a high‐quality InN film grown on GaN

“…The HVPE GaN template has been compensated with Zn introduced during growth to suppress unintentional n-type conductivity. Its thickness is around 16 µm with 300 K resistivity up to 10 9 Ω.cm and dislocation density around 5×10 8 cm -2 . The InN film is n-type and has an electron density of 17 …”

“…The laser, which has a pulse width of FWHM @ 60 ps, photon energy of 2.34 eV, a repetition rate of 76 MHz, was used to both excite and probe the InN sample. The single-particle scattering (SPS) spectra were taken in the ( ) , Z X Y Z scattering configuration where X = (100), Y = (010), Z = (001) so that only the SPS spectra associated with spin-density fluctuations were detected [9,10]. The backward-scattered Raman signal was collected and analyzed by a standard Raman system consisting of a double spectrometer, a photomultiplier tube and the associated computer-controlled photon counting setup.…”

Transient picosecond Raman studies of electron and hole velocity overshoots in a GaAs-based p–i–n semiconductor nanostructure

“…The transport properties of the charge carriers, electrons and holes, are determined by many factors; among them, electric field intensity plays an important role. Under very high electric field intensity, the carrier transient transport phenomenon, which normally lasts for one picosecond or less, has been demonstrated to exhibit drastically different behaviour from that of the steady state [1][2][3][4][5].…”