The two-dimensional (2-D) quantum-well (QW) laser diode simulator Minilase-II is presented in detail. This simulator contains a complete treatment of carrier dynamics including bulk transport, quantum carrier capture, spectral hole burning, and quantum carrier heating. The models used in the simulator and their connectivity are first presented. Then the simulator is used to demonstrate the effects of various nonlinear processes occurring in QW lasers. Finally, modulation responses produced by Minilase-II are compared directly with experimental data, showing good quantitative agreement.

Simulation of carrier transport and nonlinearities in quantum-well laser diodes

The properties of hot electrons in systems where electrons and phonons experience quantum confinement are reviewed. The modifications to the behaviour of electrons and phonons brought about by confinement are described, particularly with reference to the principal scattering mechanism. The latter include the interaction with longitudinal optical phonons and plasmons, along with carrier-carrier effects. Some conflict in the literature concerning Fuchs-Kliewer polaritons is discussed. Low-temperature interactions with acoustic phonons are described. A central topic is that of energy relaxation, and the experimental and theoretical data relating to this form a large part of the review. Energy relaxation mechanisms in the femtosecond to nanosecond regimes, including intersubband and well-capture processes, are eventually summarized. An equally large section deals with hot-electron transport; in which negative differential resistance and other instabilities associated with parallel transport are discussed before turning to ballistic transport and impact ionization.

https://iopscience.iop.org/article/10.1088/0034-4885/54/2/001/pdf

Hot electrons in low-dimensional structures

Recent experiments1–6 have shown that ultrafast optical excitation of semiconductors can produce oscillating changes in the optical properties of the material. The frequency of the oscillations in transmission or reflection always matches one of the optical phonon modes, which indicates that the phonon mode becomes coherently excited. This phenomenon has been observed in GaAs,1,2 Ge,3 as well as in a variety of other less common materials.4,5 Very recently, Dekorsy and co-workers7 have also observed terahertz radiation from coherent phonons in Te.

Theory of coherent phonon oscillations in semiconductors.

Subpicosecond time-resolved Raman spectroscopy has been used to measure the lifetime of the LO phonon mode in GaN for photoexcited electron-hole pair density ranging from 1016to2×1019cm−3 The lifetime has been found to decrease from 25ps, at low density, to 035ps, at the highest density The experimental findings should help resolve the recent controversy over the lifetime of LO phonon mode in GaN

/pdf/subpicosecond-time-resolved-raman-studies-of-lo-phonons-in-4ljkvef6rg.pdf

Subpicosecond time-resolved Raman studies of LO phonons in GaN: Dependence on photoexcited carrier density

In this paper, thermal conductivity of crystalline GaAs is calculated using first-principles lattice dynamics. The harmonic and cubic force constants are obtained by fitting them to the force-displacement data from density functional theory calculations. Phonon dispersion is calculated from a dynamical matrix constructed using the harmonic force constants and phonon relaxation times are calculated using Fermi's Golden rule. The calculated GaAs thermal conductivity agrees well with experimental data. Thermal conductivity accumulations as a function of the phonon mean free path and as a function of the wavelength are obtained. Our results predict a significant size effect on the GaAs thermal conductivity in the nanoscale. Relaxation times of optical phonons and their contributions from different scattering channels are also studied. Such information will help the understanding of hot phonon effects in GaAs-based devices.

/pdf/gallium-arsenide-thermal-conductivity-and-optical-phonon-6b9xub5wbj.pdf

Gallium arsenide thermal conductivity and optical phonon relaxation times from first-principles calculations

The details of the initial relaxation of optically injected hot carriers in polar semiconductors are studied by Raman scattering from nonequilibrium LO phonons and anti-Stokes hot luminescence. Experiments on intrinsic and doped GaAs reveal carrier-phonon and carrier-carrier interaction times, the wavevector dependence of the hot phonon distribution, and the influence of holes on the LO phonon lifetime. Studies in AlxGa1−xAs probe the influence of alloy disorder on the generation of hot phonons. In addition, because there are two optic phonon modes in AlxGa1−xAs, we can experimentally measure the effect of ionicity (the frequency difference between LO and TO phonons) on the generation rate for the hot phonons.

J.C. Tsang

Papers

Secondary emission studies of hot carrier relaxation in polar semiconductors