ON THE RELATION BETWEEN LOW-TEMPERATURE EPITAXIAL-GROWTH CONDITIONS AND THE SURFACE-MORPHOLOGY OF EPITAXIAL SI AND SI1-XGEX LAYERS, GROWN IN AN ULTRAHIGH-VACUUM, VERY-LOW PRESSURE CHEMICAL-VAPOR-DEPOSITION REACTOR

In this paper we describe the intimate relation between the surface mo rphology of epitaxial Si and Si1-xGex layers and the pressure during g rowth. All the experiments were done at a temperature of 625-degrees-C and the pressure was varied between 10(-4) and 2 x 10(-1) Torr. The l ayers were grown in an ultrahigh vacuum very low pressure chemical vap our deposition reactor (UHV-VLPCVD) with a gas mixture of SiH4 and GeH 4 without the addition of H-2. Based on the pressure and the growth-in itiating conditions, we distinguish two different growth modes, based on a different surface morphology and growth rate. The first mode (mod e I) is characterized by a high growth rate and good surface morpholog y, whereas in mode II the growth rate is significantly lower and the s urface morphology substantially rougher. We present also a qualitative explanation for these observations in terms of hydrogen coverage and impingement rate of precursor molecules on the growing crystal surface .