Hot-electron relaxation via optical phonon emissions in GaAs/AlxGa1-xAs quantum well structures: dependence upon the alloy composition and barrier width

We present a systematic investigation of the dependence of the hot-electron -optical-phonon interactions on Al composition and barrier width in GaAs/Al xGa1-xAs MQW structures. Raman scattering measurements at 15 K are presente d for samples with different barrier widths and Al composition. The optical phonon energies emitted by the photoexcited electrons in quantum wells wer e also determined by using hot-electron-neutral acceptor luminescence techn iques. It is shown that the relaxation of hot electrons in the quantum well s is dominated by the GaAs LO phonon emission for small x, but by AlAs-like LO phonons for larger Al composition. For samples with larger barriers, th e electrons in the GaAs layer relax mostly through the AlAs-like optical ph onon emission. However, in samples with smaller barriers, the relaxation of hot electrons is dominated by the GaAs optical phonon emission.