Negative differential resistance in a strained-layer quantum-well structure with a bound state

Strained-layer resonant tunneling structures of pseudomorphic GaAs-AlAs-In0.09Ga0.91As-AlAs-GaAs are studied both experimentally and with a simple quantum mechanical model. The energy spectrum of the unbiased structure includes the usual resonant states and also bound states due to the narrow-band gap InGaAs well. Strong tunneling (and negative differential resistance) are observed for the resonant states. We observe for the first time tunneling associated with a ‘‘bound-state’’ energy level which result in a zero differential conductance feature. Qualitative agreement between the experimental and calculated results are shown.