Terahertz intersubband electroluminescence from ZnO quantum cascade structures

Terahertz intersubbband electrolulminescence from ZnO quantum cascade structures, based on four quantum well per period, is presented. The whole cascade structure was grown on the m-plane ZnO substrate. An electroluminescence peak with a linewidth of ~ 20 me V is observed at 8.5 THz, in consistent with the numerical simulation by a density matrix model.