Diagonal and vertical far-infrared transitions from quantum cascade emitters

We report a study of a far-infrared GaAs-Al/sub 0.15/Ga/sub 0.85/As quantum cascade electro-luminescence device designed to emit via both diagonal and vertical transitions. Each type of transition was preferentially chosen by varying the applied electric field. The different transitions were identified by correlation with bandstructure calculations, electrical characteristics and the width of the peaks. Further, the importance of contact resistance on the spectra was shown.