Hot electron spectroscopy of carrier relaxation within indirect AlAs tunnel barriers

Hot electron spectroscopy has been performed on electrons which have tunnel ed through indirect AlAs potential barriers in a tunneling hot electron tra nsfer amplifier. We find that only about 1% of the electrons are collected close to their injection energy in stark contrast to an otherwise identical structure with an Al0.5Ga0.5As barrier where this fraction was 30%. Measur ements under hydrostatic pressure show clear evidence for the real-space tr ansfer of electrons from the emitter electrode into an X-point barrier subb and adjacent to the emitter Fermi band. A detailed analysis of hot electron spectra reveals that the transferred electrons undergo strong inelastic sc attering within the AlAs barrier and relax down through the ladder of X-poi nt subbands there before being reemitted into the base layer. (C) 1999 Amer ican Institute of Physics. [S0003-6951(99)05048-2].