We have studied acoustic phonon-assisted tunneling in a weakly coupled GaAs/AlAs superlattice (SL) in a magnetic field. At zero magnetic field, the phonon-assisted tunnel current, $\delta I$, exhibits maximum at a particular value of the Stark splitting, ${\Delta }_{\text{max}}$, which depends on the spectral distribution of the nonequilibrium phonons. Applying the field $\left(B\le 7\text{T}\right)$ perpendicular to the SL growth direction, $z$, had no significant effect on the phonon-assisted tunneling current compared to $B=0$. However, in a magnetic field parallel to $z$, ${\Delta }_{\text{max}}$ is proportional to $B$ and weakly dependent on the phonon spectrum. This behavior, which we explain in terms of the momentum selection rules for phonon-assisted transitions in a magnetically quantized electron system, suggests that phonon amplification in the SL can be tuned by the magnetic field.

• Received 28 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.035335