Far-infrared electroluminescence from parabolic quantum well superlatticesexcited by resonant tunneling injection

We present an investigation of intersubband emission at far-infrared wavele ngths from semiconductor superlattices with parabolically graded quantum we lls. Light emission is produced by sequential resonant tunneling injection of electrons into higher energy levels of the quantum wells and subsequent radiative decay. The current versus voltage curves of these devices exhibit negative differential resistances characteristic of the sequential resonan t tunneling injection. A single, narrow emission peak is observed from the superlattices with parabolic quantum wells demonstrating radiative decay th rough multiple evenly spaced energy levels. When a chirped superlattice act ing as an electron energy filter replaces the barrier in each period of the structure, clearer resonances are observed in the current-voltage characte ristics and more efficient injection is achieved. (C) 2000 American Institu te of Physics. [S0021-8979(00)02913-3].