MIGRATION-ENHANCED PULSED CHEMICAL BEAM EPITAXY OF GAP ON SI(001)

In this paper, we present results on the heteroepitaxial growth of GaP on Si by migration enhanced pulsed chemical beam epitaxy (PCBE) using additional hydrogen and filament assisted techniques. For the real-ti me monitoring we applied a new technique, p-polarized reflectance spec troscopy (PRS) which provides information on the bulk, interface and s urface properties of the grown GaP/Si heterostructures. The monitoring is initiated close to the Brewster angle for the substrate material, achieving high sensitivity in the initial phase of heteroepitaxial ove rgrowth. The bulk properties and growth rate are monitored using the q uarter wave periodic structure in the reflectance based on interferenc e in the film. The surface vicinity properties are monitored by the pe riodic fine structures in the intensity of the reflected light, which are correlated with the switching cycles of the metalorganic precursor pulses and are amplitude-modulated in accord with the repeat cycle of the heteroepitaxial growth process. Additional information regarding the surface roughness was revealed by scattered light measurements dur ing the growth of the film. The results of real-time monitoring of nuc leation and growth are combined with results of the ex-situ characteri zation of the GaP/Si heterostructure by cross-sectional transmission e lectron microscopy (TEM) and atomic force microscopy (AFM) studies to gain an understanding of the critical phase, in which the silicon surf ace becomes sealed by a contiguous epitaxial film of GaP. The defects formed in the GaP film during this phase determine the quality of the epilayers obtained upon prolonged growth.