GROWTH AND PHOTOLUMINESCENCE CHARACTERIZATION OF PSEUDOMORPHIC SIGE SINGLE QUANTUM-WELLS

We report on MBE growth and photoluminescence characterization of single Si1-xGex quantum wells grown pseudomorphically on Si(100) substrates. Growth temperature T(G), Ge content x, and quantum well thickness L(z) were varied in a systematic study. x and L(z) were determined by 5-crystal X-ray rocking analyses. For all growth temperatures studied (350 less-than-or-equal-to T(E) less-than-or-equal-to 750-degrees-C) we find SiGe bandedge luminescence consisting of a no-phonon (NP) line and four well-resolved phonon replicas. In most samples, only the free exciton but no bound exciton appeared in the spectra, which is indicative of a low background impurity level. Line widths down to 2.9 meV for the NP line were observed. The bandedge luminescence could be followed down to excitation power densities as low as 0.1 mW/cm2. The broad luminescence band located about 150 meV below the SiGe bandgap, which has been reported as a typical feature of MBE grown material, is virtually absent in our samples independent of the growth temperatures employed.