Electrooptical properties of the Si δ-doped GaAs/AlGaAs triple-barrier resonant tunneling structure

The electrooptical properties of a Si δ-doped GaAs/Al_0.3Ga_0.7As triple-barrier resonant tunneling (TRT) nanostructure have been studied by photoreflectance spectroscopy from 20 K to room temperature. The TRT structure forms two coupled quantum wells. The first and the second electronic subbands in the wide well are partially filled, and the corresponding optical transitions are suppressed. The strongest spectral feature is due to the enhancement of the subband resonance between the two coupled wells. The ionized δ-doping centers in the Al_0.3Ga0.7As side barriers can induce internal electric fields, and cause oscillatory spectral features when the photon energy is larger than the gap of Al_0.3Ga_0.7As. Analyzing the oscillatory part of the spectrum gives an internal electric field of 32 kV/cm, and an estimation of the electron subband energy in the ionized δ-doping center induced potential wells.