Passivation of GaAs (100) with an Adhesion Promoting Self-Assembled Monolayer

Abstract

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.

Study of SiO2/Si Interface by Surface Techniques

“…The As signal from TOA: 15 0 is the most sensitive to the surface structure, due to a similar peak intensities arising from oxide (interface) and volume (GaAs).As presented in Fig.7 at small analysis angles the As and Ga concentrations grows and at the most surface sensitive angle the concentration of C and O is higher than the concentrations for As and Ga. For the native oxidized sample the atomic surface composition Ga/As ratio is related to the entire signal arisen from surface and volume. The Ga signal arises from 19.1 eV (GaAs) and 20.3 eV (Ga 2 O 3 ) [27]. The As to Ga ratio in the bulk is close to a stoichiometric value of 1.05.…”

Corrosion Protection and Long-Term Chemical Functionalization of Gallium Arsenide in an Aqueous Environment

“…The significant initial improvement of the photoluminescence intensity was found to decay only over the course of several days to weeks, in a controlled argon atmosphere, and MPT polymerization further increased the observed degradation times by about one order of magnitude. [28] However, whereas deterioration of the GaAs surface was generally avoided more effectively when the polymerized overlayer rather than non-polymerized MPT was used, the difference was not as pronounced under ambient conditions (i.e., in humid air).…”

Enabling Long-Term Operation of GaAs-Based Sensors

“…After etching, the substrates are dried with nitrogen and immersed immediately in ethanol solutions of MPTMS; in previous works either 0.3 vol.% (16 mM) [11], or 0.4 vol.% (21.5 mM) [12] concentrations were used. Placing in a water bath at 50°C for 4 hours allows primary MPTMS layer adsorption with thiol binding to the substrate and with the reactive methoxy groups pointing outwards [22]. Polymerization of MPTMS is initiated by adding NH 4 In order to estimate the thickness of the polymer, GaAs samples were covered with MPTMS film in pa- When an MPTMS layer is deposited by the regular procedure (see Materials and Methods), the GaAs substrate exhibits good corrosion stability when exposed to an aqueous environment for up to 24 hours [11,23].…”

“…Hou et al [22] employed chemical cross-linking of (3-mercaptopropyl)-trimethoxysilane (MPTMS) after depositing MPTMS SAM on GaAs in order to improve the stability of the coating. This idea was further developed by Kirchner et al [23] to achieve functionalization of the GaAs surface by polymerization of MPTMS in a solution sol-gel process.…”