Ultrafast acoustic strain generation and effects in semiconductor nanostructures

摘要: The nature of ultrafast acoustic strain generation and effects in III-V semiconductor-based nanostructures is explored this thesis via experimental observations that are supported by theoretical analysis. Specifically, coherent phonon processes bulk gallium arsenide (GaAs) investigated through remote hypersonic detection using a double quantum well-embedded p-i-n diode, after which strain-induced barrier well resonant tunnelling diode examined. Finally, preliminary studies on modulation dot also considered, with recommendations for future experimentation. It was experimentally observed the transduction GaAs produces an initial wavepacket strongly asymmetric heavily damped leading edge. This determined to be due photogeneration supersonically expanding electron-hole plasma near irradiated surface. Coupled its propagation from free surface, generates stress therefore system caused combination deformation potential thermoelasticity; former latter shown dominant low high optical excitation densities, respectively. These waves cannot escape until it has decelerated subsonic velocities, achieved finite time, thus resulting asymmetry time reduced at densities expansion limitation increased non-radiative Auger recombination pairs. This conclusion substantiated analytical expressions derived inhomogeneous wave equation, analysis spatially- temporally-expanding density based mechanism only. Numerical simulations these fitted data, thermoelasticity contribution deduced non-linear deviation rate change duration expressed square-law behaviour parameter, attributed processes. Strain-induced resulted current picosecond timescale only when device biased within resonance region, largest modulations threshold peak biases. Through structure stationary current-voltage characteristics, demonstrated changes variations confined ground state energies itself. Numerical rates provided excellent agreement particularly comparing charge transfer rates, where limited temporal response could ignored. Furthermore, transferred set polarity regardless density, possesses “rectifying” behaviour. As such, been that, exploiting acoustoelectronic pumping effect, control or application as detector possible. In closing, mechanisms utilisation effect both exhibited work, provide promising evidence novel methods research into semiconductor nanostructures.