Acoustic phonon-assisted tunneling in GaAs/AlAs superlattices

Measurements have been made of the transient changes in tunnel current ΔI through a biassed 50 period Si doped GaAs/AlAs superlattice produced by pulses of nonequilibrium acoustic phonons. The bias Vₘₐₓ at which ΔI is greatest varies linearly with the heater temperature Tₕ and hence with the dominant phonon frequency, the SL is acting as a phonon spectrometer with a linewidth (HWHM) kBTₕ/h~200GHz (0.8 meV) for Tₕ=10K. 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 ΔI(V) are compared with values calculated using a similar model to that of Glavin et al. [JETP Lett. 51, 191 (2000)].