Coherent Acoustic Phonon Oscillations in Semiconductor Multiple Quantum Wells with Piezoelectric Fields

Abstract

Large coherent acoustic phonon oscillations were demonstrated using InGaN/GaN multiple quantum wells with piezoelectric fields. With UV femtosecond pulse excitation, photogenerated carriers screened the piezoelectric field and initiated the displacive coherent phonon oscillations. The specific phonon frequency was selected by the coupling between the periodic carrier distribution and the corresponding acoustic phonon mode. The induced acoustic phonon oscillation resulted in piezoelectric field modulation and then caused absorption variation through the quantum confined Franz-Keldysh effect. The wave vector uncertainty due to the finite sample width was found to determine the observed dephasing time.

Femtosecond pump-probe spectroscopy of propagating coherent acoustic phonons inInxGa1−xN∕GaNheterostructures

“…1 Strong coherent acoustic phonon oscillations have recently been detected in InGaN/GaN multiple quantum wells. 2,3 These phonon oscillations were much stronger than folded acoustic phonon oscillations observed in other semiconductor superlattices. 4,5,6 InGaN/GaN heterostructures are highly strained at high In concentrations giving rise to large built-in piezoelectric fields, 7,8,9,10 and the large strength of the coherent acoustic phonon oscillations was attributed to the large strain and piezoelectric fields.…”

“…4,5,6 InGaN/GaN heterostructures are highly strained at high In concentrations giving rise to large built-in piezoelectric fields, 7,8,9,10 and the large strength of the coherent acoustic phonon oscillations was attributed to the large strain and piezoelectric fields. 2 In this paper, we report the generation of strong localized coherent phonon wavepackets in strained layer In x Ga 1−x N/GaN epilayers and heterostructures grown on GaN and Sapphire substrates. 11 By focusing high repetition rate, frequency-doubled femtosecond Ti:Sapphire laser pulses onto strongly strained InGaN/GaN heterostructures, we can, through the carrier-phonon interaction, generate coherent phonon wavepackets which are initially localized near the epilayer/surface but then propagate away from the surface/epilayer and through a GaN layer.…”

Coherent Spin and Quasiparticle Dynamics in Solution‐Processed Layered 2D Lead Halide Perovskites

“…We further speculate that the coherent distortion of the lattice by phonons changes the eigenenergies of the excitons, resulting that in exciton energy oscillations via Raman tensor 36. However, we do not rule out the possibility of other mechanisms, e.g., piezoelectric modulation 37. But this is beyond the scope of this work.…”

Picosecond Acoustics in Single Quantum Wells of Cubic GaN/(Al,Ga)N

“…If also in-depth information is required, an established technique is based on exploiting buried semiconductor quantum wells (QWs) [3][4][5]. Nitride semiconductor QWs [e.g., GaN=ðInGaÞN] are highly efficient nanostructures for the generation and detection of coherent phonons with frequencies of up to 2 THz [6]. Most of the experiments with nitride quantum wells are performed on multiple QWs based on wurtzite (hexagonal) h-GaN and its alloys.…”