Real-time optical monitoring of GaxIn1-xP and GaP heteroepitaxy on Si under pulsed chemical beam conditions

In this paper we describe the combined application of p-polarized reflectance spectroscopy (PRS), reflectance difference spectroscopy (RDS), and laser light scattering (LLS) to investigate the growth of GaxIn1-xP/GaP on Si by pulsed chemical beam epitaxy (PCBE) with tertiarybutylphosphine, triethylgallium, and trimethylindium precursors, The pulsed supply of chemical precursors causes a periodic alteration of the surface composition, which is observed as corresponding periodicity (fine structure) in the RD and PRS signals, confirming the high sensitivity of both methods to surface chemistry during the entire growth process. This fine structure is modeled under conditions where the surface chemistry periodically alternates between a four-layer stack (ambient/surface layer/film/substrate) and a three layer stack (ambient/film/substrate) description with a corresponding alteration in the optical response of the PRS and RD signals. RD spectra are used to estimate the surface reconstruction of the layers, LLS provides information about the surface topography and thus the evolution of surface roughness, which is especially important during nucleation.