Role of ultra thin pseudomorphic InP layer to improve the high-k dielectric/GaAs interface in realizing metal-oxide-semiconductor capacitor

Abstract

In this article, we report GaAs metal-oxide-semiconductor (MOS) capacitors with a metal organic chemical vapor deposited ultrathin (1.5 nm) pseudomorphic InP interface passivation layer (IPL) and a thin (5 nm) ZrO2 high-k dielectric. Reduction of the surface states on InP passivated GaAs surfaces was observed from the photoluminescence study. The x-ray photoelectron spectra confirmed the dramatic reduction of GaAs native oxides (Ga-O and As-O) from the interface of ZrO2 and p-GaAs, implying that the Fermi level at the high-k/GaAs interface can be unpinned with good interface quality. As a result, very low values of interface trap density (1.1 × 1011 cm−2 eV−1) and hysteresis (8.21 mV) were observed. The same was done for directly deposited ZrO2 on GaAs surface to understand the efficacy of InP interface passivation layer on GaAs MOS devices. A systematic capacitance-voltage and current density-voltage studies were performed on bothAl/ZrO2/InP/p-GaAs and Al/ZrO2/p-GaAs structures. It was found that insertion of 1.5 nm InP ultrathin layer in-between ZrO2 and GaAs improves the essential parameters of GaAs MOS such as dielectric constant, frequency dispersion, leakage current, etc. The dielectric reliability has been studied with constant voltage stressing. A very small flatband voltage shift with stress time was observed in InP passivated GaAs MOS capacitors.