Photoluminescence from Si/Si1-xGex single quantum wells in high magnetic fields: localized and free exciton recombination

We have performed photoluminescence measurements on three Si/Si0.76Ge0.24 S ingle quantum wells with well widths of 2.5, 4.8 and 8.5 nm in magnetic fie lds up to B = 20 T. For the excitation and detection of the photoluminescen ce a large core (0.6 mm) glass fiber was used, which provides sufficient si gnal intensities at moderate excitation power densities. The magnetic field leads to a luminescence peak splitting and rather large diamagnetic shifts in the wider quantum wells. The increase of the diamagnetic shift with wel l width indicates a strong reduction of the exciton binding energy, which i s consistent with the previously proposed type II band alignment in these q uantum wells, and we interpret the peak splitting in terms of localized and free exciton recombination. (C) 1998 Elsevier Science B.V. All rights rese rved.