Relaxed SiGe buffer layer growth with point defect injection

Abstract

For virtual substrate preparation, we used thin relaxed SiGe buffer layer growth on Si (001) substrates by molecular beam epitaxy (MBE). Aiming to stimulate the strain relaxation and to procure the conditions for crystal structure improvement, we deliberately introduced point defects in situ, during layer growth. To generate point defects during MBE, we pursued two separate techniques, both applied during the stage of metastable pseudomorphic growth: (i) epitaxy at very low temperature and (ii) bombardment of the growth surface with Si+ ions. We studied the role of these measures and of other growth conditions in the strain relaxation processes and in the crystal structure of the SiGe buffer layers. This paper reports the successful relaxation of thin (<100 nm) Si1−xGex (x=0.25−0.7) buffer layers with epitaxy at very low temperatures. Under ion bombardment we obtained full relaxation with thin (<100 nm) Si1−xGex buffer layers for x≥0.5.