<i>I</i> <i>n</i> <i>s</i> <i>i</i> <i>t</i> <i>u</i> x-ray photoelectron spectroscopic study of remote plasma enhanced chemical vapor deposition of silicon nitride on sulfide passivated InP

Abstract

The changes in chemical composition and Fermi level position of n- and p-InP surfaces induced by reactions with sodium sulfide and ammonium sulfide solutions and with vapor from ammonium sulfide solution have been characterized by x-ray photoelectron spectroscopy (XPS). Further, in situ XPS analysis was used to study interfaces formed on sulfide passivated surfaces by remote plasma enhanced chemical vapor deposition of silicon nitride. We found that both indium and phosphorus sulfide phases were formed as a result of exposing InP to sulfide vapor at room temperature. However, most of the surface native sulfides dissolved in water and the resultant surface was then covered with about one monolayer of indium sulfide. Further, reduction in donor states in the upper band gap was evident by these sulfide treatments. However, heating the sulfide passivated sample caused an increase in surface states. Sulfur doping effect was also observed upon heating InP covered with the air oxidation products of the sulfide vapor. In the study of silicon nitride deposition, we found that the formation of native nitride could be avoided by optimizing the processing parameters. In addition, we also found that the surface native sulfide on InP reacted with the deposited silicon nitride. Capitance–voltage (C–V) data collected at 1 MHz indicate that a low interface state density could be obtained on silicon nitride/sulfide passivated InP. However, measurements of surface band bending of InP as a function of charging potential on a 10 nm silicon nitride on InP by XPS indicate that slow surface states were present which restricted changes in band bending to less than 0.3 eV when the applied voltage on the thin dielectric was −2 V.