Real-time monitoring of heteroepitaxial growth processes on the silicon(001) surface by p-polarized reflectance spectroscopy

In this paper we describe the real-time monitoring by p-polarized reflectance spectroscopy (PRS) using pulsed chemical beam epitaxy (PCBE) of GaxIn1-xP on Si(001) as an example. For constant source vapor pulse height, width and repetition rate, the formation of the heteroepitaxial film on the Si(001) surface proceeds via a three-dimensional nucleation and overgrowth mechanism. Provision of a high initial supersaturation of the surface drives the nucleation kinetics toward a two-dimensional mechanism. The analysis of the fine structure in the PRS intensity reveals that under the conditions of quasi-steady state growth the surface chemistry cycles between enhanced and diminished P-activity and diminished and enhanced Ga-activity, with the dealkylation of the group III alkyl source molecules constituting a rate limiting step in the growth kinetics. Since the deposition rate per precursor pulse cycle can be determined experimentally, molecular layer epitaxy conditions can be imposed and verified in real-time without reliance on a self-limiting growth mechanism.