OPTIMAL THICKNESS FOR SI INTERLAYER AS DIFFUSION BARRIER AT THE SI3N4/GAAS INTERFACE - A TRANSMISSION ELECTRON-MICROSCOPY STUDY

Using transmission electron microscopy, we investigate Si3N4 grown in situ on GaAs metal-insulator-semiconductor (MIS) device structures with a Si interlayer, which has been previously shown to improve the electrical properties of field-effect transistors with Si3N4 gates on GaAs. We find that the primary role of the Si interlayer is to prevent the reaction between the nitride or nitrogen used for growth and GaAs. The interlayer thickness dependence of this microstructure, and its relationship to electrical properties, are discussed. The optimal thickness of the thin pseudomorphic Si interlayer appears to be around 0.4 nm. The growth temperature dependence of the critical thickness for morphological instability is demonstrated.