Photogenerated‐carrier‐induced band bending effects on generation of a coherent longitudinal optical phonon in a GaAs buffer layer optically masked by a GaSb top epitaxial layer

Abstract

AbstractWe demonstrate that, in a GaSb/GaAs epitaxial structure, the coherent longitudinal optical (LO) phonon in a GaAs buffer layer optically masked by a GaSb top layer is observed utilizing terahertz spectroscopy. It is confirmed from Raman scattering measurements that only the optical phonons in the GaSb layer is observable. In the terahertz‐wave measurement, the Fourier power spectrum of a terahertz waveform exhibits both the coherent GaAs and GaSb LO phonon bands; namely, the coherent LO phonon in the optically masked GaAs buffer layer is observed. This fact demonstrates that the instantaneous surface potential modulation, which originates from the impulsive carrier excitation by a pump beam, reaches the GaAs buffer layer. We perform a time‐partitioning Fourier transform analysis in order to investigate the decay dynamics of the coherent GaAs and GaSb LO phonons. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)