Electronic structure of quantum-well states revealed under high pressures

✍ Scribed by D.J. Wolford; T.F. Kuech; T.W. Steiner; J.A. Bradley; M.A. Gell; D. Ninno; M. Jaros

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 995 KB
• Volume: 4
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1016/0749-6036(88)90231-5

✦ Synopsis

We report on electronic and optical properties under pressure of GaAs/AI,Ga,_,As multi-quantum-wells and superlattices versus well-width and composition x. Photoluminescence measurements are used together with full-scale pseudopotential simulation of electronic structure. Ile-Tlhh transition intensity thresholds mark level degeneracy with the AI,Ga,_,As X-band edge, shifted in the heterostructures by valence-band offset-induced staggered band alignment. In SLs, indirect-gap spatially quantized electron states formed within the subsidiary X bands are observed experimentally and modelled theoretically.

These new Xderived states are located within the Al,Ga,.,As and optical transitions occur across both k-space and the hetero-interface.

We thus obtain direct optical measure of the GaAs/Al,Ga,.,As band offsets, giving AE, = (0.32 + 0.02)AE: across the alloy system. Intervalley "mixing" connecting the quantized electron states of differing k-value is also explored, as crossings between them are induced under pressure. Energy levels, transition energies and intensities, radiative lifetimes, level pcrturbations (anticrossings), and oscillator strengths have been obtained with good agreement between experiment and theory. We show that coupling between the familiar zone-center quantum-well states and the new zone-edge states is significant and observable, and must be taken into account for full description of quantum-well states in multi-valley semiconductors.