STRESS EFFECTS INDUCED IN SIGE STRAINED LAYERS BY LOW-TEMPERATURE ULTRAVIOLET-ASSISTED OXIDATION

Low-temperature (550 degrees C) ultraviolet-assisted oxidation of epit axially grown Si0.8Ge0.2 strained layers on (100)Si substrates leads t o the formation of nanocrystalline Ge (nc-Ge) particles embedded in a SiO2 layer which exhibit visible photoluminescence with an emission ma ximum situated at around 2.18 eV. Grazing incidence x-ray diffraction investigations of the remaining SiGe layer which was continually rejec ted by the advancing oxide layer have shown the presence of the (311) diffraction peak. This implies that the unoxidized SiGe layer has been fractured in many regions misoriented with respect to the initial lay er. The displacement of the SiGe (311) peak position recorded for samp les which had their grown oxide layer stripped away when compared with as-grown samples indicates the presence of a significant stress in th ese low-temperature grown oxide layers. This stress is believed to exp lain both the survival of the nc-Ge particles during prolonged oxidati on and the fracturing of the buried SiGe layer. (C) 1998 American Inst itute of Physics. [S0021-8979(98)01603-X].