Semi-analytical modeling of Ag and Au nanoparticles and fullerene (C60) embedded gate oxide compound semiconductor MOSFET memory devices

摘要

In this paper we present an analytical simulation study of Non-volatile MOSFET memory devices with Ag/Au nanoparticles/fullerene (C60) embedded gate dielectric stacks. We considered a long channel planar MOSFET, having a multilayer SiO_2-HfO_2 (7.5 nm)-Ag/Au nc/C60 embedded HfO_2(6 nm)-HfO_2 (30 nm) gate dielectric stack. We considered three substrate materials GaN, InP and the conventional Si substrate, for use in such MOSFET NVM devices. From a semi-analytic solution of the Poisson equation, the potential and the electric fields in the substrate and the different layers of the gate oxide stack were derived. Thereafter using the WKB approximation, we have investigated the Fowler-Nordheim tunneling currents from the Si inversion layer to the embedded nanocrystal states in such devices. From our model, we simulated the write-erase characteristics, gate tunneling currents, and the transient threshold voltage shifts of the MOSFET NVM devices. The results from our model were compared with recent experimental results for Au nc and Ag nc embedded gate dielectric MOSFET memories. From the studies, the C60 embedded devices showed faster charging performance and higher charge storage, than both the metallic nc embedded devices. The nc Au embedded device displayed superior characteristics compared to the nc Ag embedded device. From the model GaN emerged as the overall better substrate material than Si and InP in terms of higher threshold voltage shift, lesser write programming voltage and better charge retention capabilities.