ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
We use the semiempirical tight binding method with an sp3s* basis and second-nearest-neighbor interactions to investigate the electronic structure of (GaAs)m/(Ge2)n (001) superlattices (SLs) with 1≤(m,n)≤20. We have found no correspondence between the calculated band structures of these (GaAs)/(Ge2) SLs and those for (GaAs)1−x(Ge2)x random alloys. The inclusion of second-nearest-neighbor, compared with the nearest-neighbor interactions, raised the SL band gap for (m,n)〉1, while lowering that for m=n=1. For the (GaAs)20/(Ge2)20 (001) SLs our calculation gives a band gap energy of 0.79 eV, while for (GaAs)1/(Ge2)1 the band gap energy is 0.11 eV. For small values of m, the (GaAs)m/(Ge2)n SLs are predicted to have indirect band gaps regardless of the valence band offset used in the calculation. For larger values of m, however, the predicted SL band gaps become direct for large values of valence band offset. For ΔEv=0.85 eV we find a direct to indirect band gap transition for m between 14 and 16. In the indirect-gap SLs, the electrons and holes are confined in the Ge layers, while the direct-gap SLs have holes confined in the Ge layers and electrons in the GaAs layers. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.364137
