Interaction of a strongly coupled superlattice with terminating quantum wells

Quantum wells are used to terminate the periodicity of a tightly coupled superlattice. When an electric field is applied, the quantum wells can interact with either the conduction or valence bands of the superlattice, depending upon the direction of the field, and whether the quantum wells are right-end or left-end terminations of the superlattice. We monitor the quantum-well–superlattice interactions with photocurrent spectroscopy at 77 K. Quantitative analysis of the conduction- or valence-band quantum-well–superlattice interactions depends sensitively on the band-offset ratio. The conduction-band and valence-band offsets are determined separately and used to test the validity and utility of an empirical two-band effective-mass model for analysis of complex heterostructures with both thick (∼100 Å) and thin (∼20 Å) layers.