Abstract
Low-temperature (1.8 K) optical reflectivity measurements have been carried out to identify the principal interband transition energies in ordered quantum well (QW) samples. To account for ordering effects on the band offset and optical transition energy, a theoretical model has been constructed by incorporating the CuPt-type ordering effects of band-gap reduction and valence-band splitting into the model-solid theory. Fitting of the observed transition energies to the calculations indicates that the model can reasonably describe the band-to-band transitions in the ordered QW’s. Conclusions are reached that show that (i) ordering parameters in the QW’s can be estimated with the first band-to-band transition energy. (ii) Among the values available in the literature, two combinations of -0.43 eV/0.16 eV and -0.471 eV/0.20 eV lead to good descriptions of the lattice-matched QW’s. For the compressively strained samples, however, a smaller absolute value of is favorable. Compressive strain tends to weaken the ordering effects. (iii) For a disordered and lattice-matched/compressively strained QW, the conduction-band-offset ratio has a nearly constant value of (iv) Ordering causes an increase in and for lattice-matched and compressively strained QW’s falls in a range of as changes from 0 through 1. The influence is checked by using different values of the valence- and conduction-band deformation potentials in the calculations. A comparison of is also made with previously reported values.
- Received 24 September 2001
DOI:https://doi.org/10.1103/PhysRevB.66.035109
©2002 American Physical Society