Experimental results on phonons in semiconductor super-lattices are almost all from Raman scattering measurements. The superlattice system most studied is GaAs-Ga 1-x Al x As, and in the best-understood geometry the phonons are longitudinal modes with wave vectors perpendicular to the

Phonons in semiconductor superlattices

Spectroscopy of hot carriers in semiconductors

Raman spectroscopy of vibrations in superlattices

Long lasting RHEED oscillations during MBE growth of GaAs and AlxGa1-xAs are observed. Using these oscillations, accurate measurements of GaAs, AlxGa1-xAs growth rates and the Al mole fraction x were performed during the growths. The phase of the RHEED oscillations was analyzed by computer and molecular beam shutters were operated at a particular phase. This computer controlled phase-locked epitaxy (PLE) was applied to grow precisely defined (GaAs)2(AlAs)2 bi-layer superlattices. Raman scattering spectra showed split lines characteristic of superlattices. This PLE method is invulnerable to molecular beam fluctuations.

https://iopscience.iop.org/article/10.1143/JJAP.23.L657/pdf

Phase-Locked Epitaxy Using RHEED Intensity Oscillation

Phonons in GaAs-AlxGa1−xAs superlattices

Raman experiments on polar phonons in GaAs‐Ga1−xAlxAs superlattices are reported. Other data from the literature, and its interpretation in terms of folding of the phonon Brillouin zone and scattering from q≠0 phonons induced by electronic zone folding, are discussed. An alternative explanation is presented based on optical anisotropy induced by layering. Numerical results show good agreement with experiment.

H. Morkoc

Papers

Raman scattering in superlattices: Anisotropy of polar phonons