Electron paramagnetic resonance study of defects in oxidized and nitrided porous Si and Si1-xGex

Point defects in bulk Si have been studied for over thirty years and a very detailed understanding of their microscopic structure and electronic properties has been achieved. The recent development of porous Si has allowed a further advancement in Si related defect studies, which will be reviewed here. Two aspects of porous Si have turned out to be of particular importance for defect studies by the magnetic resonance techniques: the larger number of nanocrystals contained in a cubic millimeter sized sample and the high internal surface area with values up to 1000 m(2) cm(-3). The first allows classical EPR studies of defects in nanocrystals and the second the observation of interfacial defects under highly improved conditions. We present recent results on donor defects in nanocrystalline Si, detailed EPR and ENDOR measurements of the P-b center in Si/SiO2 prepared by native, thermal and anodic oxidation, the study of the O-17 superhyperfine interaction of the P-b center in isotopically enriched samples, the study of the P-b1 center, the dominant interface defect at (100) Si/SiO2 interfaces, as well as of the native defect structure in very thin (approximate to 20 Angstrom) thermal oxides and nitrides. First results on interfacial defects in oxidized SiGe epitaxial layers will also be reported.