Epitaxy of carbon-rich silicon with MBE

Abstract

At high concentrations, carbon in silicon shows some properties of technological interests like gap engineering, lattice engineering or the reduction of the so-called ‘Transient Enhanced Diffusion’ of some dopants. The carbon incorporation in concentrations above 1% is nevertheless a difficult task due to the low carbon solubility in silicon. Here, we present a systematic approach of the Si 1− x C x layer growth by Molecular Beam Epitaxy (MBE). To study the influence of the growth temperature on the carbon incorporation, we deposit 100 nm thick silicon layers with different carbon concentrations separated by a 100 nm silicon spacer for different temperatures, ranging from 370 up to 800 °C. In-situ Reflection High Energy Diffraction (RHEED), Secondary Ion Mass Spectroscopy (SIMS) and cross-sectional Transmission Electron Microscopy (TEM) have been performed to characterize the as-grown structures. We show the presence of two distinct growth phenomena, a ‘classical’ one, around 450 °C, where carbon is mainly substitutionally incorporated, defect free until 2%; and a second one, above 550 °C, showing an agglomeration of carbon in thin layers with presumably a very high local concentration, without any planar defects. We propose in this work a diagram of Si:C growth by MBE.