Experimental evidence of Bragg confinement of carriers in a quantum barrier

摘要: Trapping of earners over a quantum barrier by use of two superlattice (SL) sections separated by a wide spacer barrier layer has been proposed recently. 1 Proper design can lead to a quantum state, that is mostly confined to the spacer region. In the conduction (valence) band, the proposed quantum state has a discrete energy level higher.(lower) than the band edge of the spacer barrier. Since this level corresponds to the first SL's mini-stop band, the SLs act as Bragg reflectors, leading to spatial localization of the carrier wave functions. A pre-requirement for the existence of the new quantum state is that the carrier wavefunction maintains its coherence over many SL periods.