  The transport in double-barrier heterostructures of electrons interacting
with longitudinal optical phonons in the presence of parallel electric and
magnetic fields is analyzed theoretically with the aid of a 3-dimensional
quantum transport simulator. Inter Landau state transitions induced by
LO-phonon scattering-assisted resonant-tunneling is shown to be an important
process with a probability comparable to that of intra Landau state scattering.
Analysis of the current-voltage characteristics reveals also that the current
peak is a periodic function of the inverse of the magnetic field, with a period
dependent on the quasi-resonant energy level.
