PHOTOLUMINESCENCE IN UHV-CVD-GROWN SI1-XGEX QUANTUM-WELLS ON SI(100) - BAND ALIGNMENT VARIATION WITH EXCITATION DENSITY AND APPLIED UNIAXIAL-STRESS

New photoluminescence data are presented which show an intrinsic condu ction band alignment in Si1-xGex quantum wells grown by ultra-high vac uum chemical vapor deposition (UHV-CVD) on Si(001) such that the Si1-x Gex layers form electron barriers (type 11 band alignment). The variat ion of the photoluminescence peak energies with applied (110) tensile stress for various excitation intensities for a number of quantum well samples of different germanium concentration shows an intrinsic condu ction band offset which increases with germanium concentration. At hig her excitation densities a photo-induced type I band alignment was obs erved with electrons confined to the Si1-xGex layers through the elect rostatic interaction with the excitation-created holes. Supporting tem perature dependence data are also presented. (C) 1998 Elsevier Science S.A. All rights reserved.