Acoustic phonon-assisted tunneling in GaAs/AlAs superlattices

Measurements have been made of the transient changes in tunnel current DeltaI through a biassed 50 period Si doped GaAs/AlAs superlattice produced by pulses of nonequilibrium acoustic phonons. The bias V-max at which DeltaI is greatest varies linearly with the heater temperature T-h and hence with the dominant phonon frequency, the SL is acting as a phonon spectrometer with a linewidth (HWHM) less than or similar tok(B)T(h)/hsimilar to200 GHz (0.8 meV) for T-h=10 K. The spectral response was confirmed using the phonons that are scattered and hence delayed in their passage across the substrate as a source of higher average frequency than those crossing ballistically. The measured values of DeltaI(V) are compared with values calculated using a similar model to that of Glavin [JETP Lett. 51, 191 (2000)].