Coupled Bloch-Phonon Oscillations in Semiconductor Superlattices

Abstract

We investigate coherent Bloch oscillations in GaAs͞Al x Ga 12x As superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be tuned into resonance with the optical phonon. Close to resonance a direct coupling of Bloch oscillations to LO phonons is observed which gives rise to the coherent excitation of LO phonons. The density necessary for driving coherent LO phonons via Bloch oscillations is about 2 orders of magnitude smaller than the density necessary to drive coherent LO phonons in bulk GaAs. The experimental observations are confirmed by the theoretical description of this phenomenon [A.W. Ghosh et al., Phys. Rev. Lett. 85, 1084(2000].

Coherent and ultrafast optoelectronics in III–V semiconductor compounds

“…Also Bloch oscillations, as a coherent excitation in a superlattice, are able to couple to fundamental excitations of the semiconductor, such as plasmons and phonons [24]. If they are tuned into resonance with the optical phonon, Bloch oscillations provide an effective driving force for coherent lattice dynamics in a semiconductor superlattice [25].…”

Gustav‐Hertz‐Preis: Bloch‐Oszillationen und ihre Kopplung an optische Phononen: Die Femtosekunden‐Spektroskopie liefert neue Einblicke in die Dynamik von Halbleiter‐Übergittern

“…Die experimentellen Untersuchungen führten wir kürzlich in einem Übergitter mit 60 meV elektronischer Minibandbreite durch [16]. Abbildung 7 zeigt die zeitaufgelösten Daten und deren Fouriertransformierte bei einer Gittertemperatur von 10 K. Deutlich ist die Zunahme der Bloch-Frequenz mit der an das Übergitter angelegten Spannung zu sehen.…”

Well‐width dependence of coupled Bloch‐phonon oscillations in biased InGaAs/InAlAs superlattices

“…This amplitude increase is attributed to the resonant coupling of the coherent electronic carrier motion, i.e. the BO's, to the phonon oscillations via their polarization components parallel to the growth direction of the superlattice [5]. Thus, BO's appear as an highly effective driving force for the generation of coherent phonons even at low excitation densities.…”

“…Recently, the resonant coupling between optical phonons and BO's has been demonstrated for the first time in GaAs/AlGaAs superlattices [5]. Here, we present a study on coupled Bloch-phonon oscillations in In 0.53 Ga 0.47 As / In 0.52 Al 0.48 As superlattices of different well widths but constant electronic miniband widths.…”

“…In biased superlattices, the coherent superposition of electronic Wannier-Stark (WS) states by ultrashort laser pulses leads to the formation of an electronic wave packet oscillating with a frequency ν BO = eF d/h. This frequency is determined by the externally applied electric field F , the superlattice period d, the electron charge e, and Planck's constant h.Recently, the resonant coupling between optical phonons and BO's has been demonstrated for the first time in GaAs/AlGaAs superlattices [5]. Here, we present a study on coupled Bloch-phonon oscillations in In 0.53 Ga 0.47 As / In 0.52 Al 0.48 As superlattices of different well widths but constant electronic miniband widths.…”