Magnetic-field-enhanced quantum-cascade emission

We have observed an enhancement of terahertz intersubband electroluminescen ce in a quantum cascade structure in the presence of a magnetic field appli ed normal to the epitaxial layers. At a field of B = 7.2 T the emission eff iciency doubles. This effect is attributed to the suppression of nonradiati ve Auger-intersubband transitions caused by Landau-quantization of the in-p lane electron motion. The magnetic field dependence of the luminescence int ensity shows strong oscillations. These magnetointersubband oscillations ar e caused by the modulation of the transition rate via resonant inter-Landau -level transfer. (C) 2000 American Institute of Physics. [S0003-6951(00)042 01-7].