INTENSE VISIBLE PHOTOLUMINESCENCE FROM MOLECULAR-BEAM EPITAXY POROUS SI1-XGEX GROWN ON SI

The observation of strong visible photoluminescence (PL) from Molecula r Beam Epitaxy (MBE) B-doped porous Si0.7Ge0.3 grown on p(-)-type Si w afers are reported. The porous layers were formed by an electrochemica l etching process with a range of preparative conditions. A significan t shift in the emission energy of porous Si0.7Ge0.3 grown on Si has be en observed for various anodization conditions and for the temperature range 295-78 K. The PL emission energy has been found to remain almos t unchanged on varying excitation energy, and to increase linearly wit h reciprocal temperature, The position of the PL emission, however, wa s observed to be strongly dependent upon the anodization current densi ty and the duration of the etching process. The origin of visible PL o f the porous MBE-SiGe films is interpreted by considering the quantum confinement effect, as in the interpretation of PL from porous Si, and the evolution of the SiGe Si-like band structure. (C) 1997 Elsevier S cience S.A.