Hot-phonon-assisted absorption at semiconductor heterointerfaces monitored by pump-probe second-harmonic generation

We provide the evidence for the hot-LO-phonon-assisted absorption at semiconductor heterointerfaces. The process is demonstrated with $\mathrm{Ga}\mathrm{As}∕\mathrm{Ga}\mathrm{Sb}$ interface when the photon energy is tuned below the band-gap energy for GaAs, but it is in a great excess for GaSb. The excitation of carriers in GaAs in the vicinity of the heterointerface is shown to be assisted by hot LO phonons generated in GaAs and GaSb within the relaxation of hot carriers in GaSb. The effect has been observed in the ultrafast pump-probe experiment through the interfacial-electric-field-induced second-harmonic generation response.