Abstract
We report high-pressure photoluminescence (PL) experiments (to at 9 K) on quantum wells (QWs) having N compositions in the dilute regime where the alloy conduction band (CB) evolves rapidly via delocalization of N-pair (cluster) states. Under increasing applied pressure, we observe low-energy broadening of the emission spectra, an increase in the Stokes shift of PL peaks relative to the QW absorption edge, and several new N-pair PL features that derive from CB-resonant states at 1 atm. Two of the latter features (assigned to replica) appear strongly in the sample at energies below the QW absorption edge for but are completely absent in the sample—an effect that has not been seen previously in alloys to our best knowledge. The trends for broadening and increase in Stokes shift under pressure are accounted for using a model of the recombination kinetics that considers competing fluctuation and N-pair states. The absence of the features in the sample provides evidence that N-pair states incorporate into the CB continuum via an energy- and/or state-selective delocalization process. The observed selectivity in the narrow composition range while bound states and other resonant states closer to the CB edge remain unaffected, offers an important test for band-structure calculations in dilute alloys. Selective delocalization of resonant N-pair states is difficult to explain within an impurity-band model, but it is qualitatively consistent with recent theoretical studies of CB formation in dilute alloys that use a full-hybridization approach to treat the incorporation of N-pair (cluster) states.
- Received 22 November 2002
DOI:https://doi.org/10.1103/PhysRevB.68.035336
©2003 American Physical Society