Enabling Long-Term Operation of GaAs-Based Sensors

Abstract

A coating scheme was developed for enabling the operation of a GaAs-based Molecular Controlled Semiconductor Resistor (MOCSER) under biological conditions. Usually GaAs is susceptible to etching in an aqueous environment. Several methods of protecting the semiconductor based devices were suggested previously. However, even when protected, it is very difficult to ensure the operation of a GaAs-based electronic sensor in aqua solution for long periods. We developed a new depositing scheme of (3-mercaptopropyl)-trimethoxysilane (MPTMS) on GaAs substrate consisting of two separate steps. The first involves chemisorption of a dense primary MPTMS layer on the substrate, whereas in the second, a thin MPTMS polymer layer is deposited on the already adsorbed layer, resulting in a 15 - 29 nm thick coating. We show that applying the new MPTMS deposition procedure to GaAs-based MOCSER devices allows up to 15 hours of continuous electrical measurements and stable performance of the sensing device in harsh biological environment. The new protection allows implementing GaAs technology in bioelectronics, particularly in biosensing.