Photocurrent oscillations by sequential phonon emission on GaAs-GaAlAs heterostructures

The authors have measured the tunnelling current of photoexcited carriers perpendicular to the GaAlAs barrier on p-GaAs-n-GaAlAs-p-GaAs heterostructures. A series of peaks is observed in the wavelength-dependent photocurrent flowing from the two dimensional electron gas through the barrier into a semitransparent contact on top of the samples. As the transmission coefficient of the GaAlAs barrier strongly depends on the energy of the incident electrons, an energy loss of photoexcited carriers by sequential phonon emission leads to oscillations in the tunnelling current.