Comment. Direct transition energies in strained ten-monolayer germanium/silicon superlattices.

Schmid U., Christensen N. E., Cardona M.

Max-Planck-Inst. Festkoerperforsch., Stuttgart , D-7000/80, Fed. Rep. Ger.

A polemic. R. Zachai et al. (ibid., 1990, 64, 1055) assigned a 0.84 eV luminescence peak from Ge4Si6 strained-layer superlattices (SLSs) to a quasidirect gap. Ab initio linear-muffin-tin-orbital calcns. of GenSim SLSs where n + m = 10 indicate they are direct-gap materials. Rather, the luminescence peak is probably recombination radiation from dislocations or possibly other defects.

Physical Review Letters, 65 2610, 1990.

Max-Planck Institut für Festkörperforschung;
Postfach 80 06 65   D-70506 Stuttgart