Observation of resonant tunnelling via first excited level in double-barrier diodes

Two clear resonance peaks for each bias direction accompanying negative differential resistance are observed in the Al0.3Ga0.7/GaAs/Al0.3Ga0.7As double-barrier diode of 24 to 26 monolayer well thickness. These two peaks are found to be the resonant tunnelling through the ground and first excited energy levels in the well.