Passivation of GaAs (100) with an adhesion promoting self-assembled monolayer

In this paper we demonstrate that photoluminescence (PL) from GaAs exposed to (3-mercaptopropyl)trimethoxysilane (MPT) exhibits a 10-fold enhancement over that of an oxidized sample. The PL enhancement is attributed to the formation of sulfur-surface bonds. We demonstrate that the MPT surface film that results from the treatment described herein is a monolayer thick by ellipsometry, and we examine the composition of the GaAs/MPT interfacial region using X-ray photoelectron spectroscopy (XPS). The XPS results indicate that the native oxide is removed by the etching procedure, and reoxidation of the surface is minimal during the subsequent deposition of MPT. The nature of the sulfur-surface bond is discussed in view of the XPS results reported here and those of previous measurements by other researchers. The self-assembled monolayers of MPT that forms on the GaAs surface leave a trimethoxy-silyl terminated surface that can be polymerized by exposure to weak acid. We demonstrate that the polymerized overlayer inhibits reoxidation of the GaAs surface better than the nonpolymerized, MPT treated surface.