Detection of a Coherent Longitudinal Optical Phonon in a GaAs Buffer Layer Optically Covered with a GaSb Top Epitaxial Layer Using Terahertz Spectroscopy

Abstract

We demonstrate that, in a GaSb/GaAs epitaxial structure, the coherent longitudinal optical (LO) phonon in the GaAs layer optically covered with the GaSb top layer is observed utilizing terahertz spectroscopy. In the terahertz‐wave measurement, the Fourier power spectrum of the terahertz waveform exhibits both the GaAs and the GaSb LO phonons; namely, the coherent LO phonon in the optically covered GaAs buffer layer is observed in the terahertz‐wave measurement. This fact demonstrates that the instantaneous surface potential modulation originating from the impulsive carrier excitation by the pump pulses reaches the GaAs buffer layer. This surface potential modulation generates the coherent GaAs LO phonon.