Comparative passivation effects of self-assembled mono- and multilayers on GaAs junction field effect transistors

Control of semiconductor interface state density with molecular passivation is essential for developing conduction- based biosensors. In this study, GaAs junction field effect transistors ( JFETs ) are fabricated and characterized before and after passivation of the GaAs surface with self- assembled mono- and multilayers. The JFETs functionalized with 1- octadecanethiol monolayers and two types of self- assembled organic nanodielectric ( SAND ) multilayers exhibit significantly different threshold voltage ( V-th ) and subthreshold slope ( S-sub ) characteristics versus the unpassivated devices and provide useful information on the quality of the passivation. Two- dimensional device simulations quantify the effective density of fixed surface charges and interfacial traps and argue for the importance of the type- III SAND ionic charges in enhancing GaAs JFET response characteristics. (C) 2008 American Institute of Physics.