Abstract: Methods and compositions are provided for planarizing a substrate with selective removal rates and low dishing, wherein the substrate comprises multiple dielectric materials, such as silicon oxide and a thin underlayer of silicon nitride used as a stop layer. One aspect of the method includes using a fixed abrasive polishing pad and at least one amino acid as a polishing fluid additive capable of significantly enhancing the polishing process. Amino acid addition in combination with fixed abrasive polishing of shallow trench isolation structures offers high topography and oxide to nitride selectivity.

Abstract: A new GaAs FET structure is provided by a process which provides a GaAs channel between AlGaAs layers and wherein the GaAs channel has a higher active carrier concentration than either adjacent AlGaAs layer.

Abstract: A high speed GaAs FET is provided by forming a sandwiched GaAs channel between AlGaAs layers and employing an Si implant to provide channel doping for the GaAs channel. The poor activation efficiency of Si in AlGaAs relative to its activation efficiency in GaAs provides a channel having a higher active dopant concentration than exists in the adjacent sandwiching layers. This tends to enhance conductivity in the channel relative to the sandwiching layers.

Abstract: A composite buffer layer is formed with a layer of GaAs on a semi-insulating GaAs substrate. Next a short period superlattice is formed followed by another GaAs layer, whereon is formed a first AlGaAs layer having a first mole fraction of Al and a second AlGaAs layer having a second mole fraction of Al higher than the first mole fraction. As intrinsic GaAs channel layer is formed on the second AlGaAs layer.

Abstract: A composite buffer layer is formed with a layer of GaAs on a semi-insulating GaAs substrate. Next a short period superlattice is formed followed by another GaAs layer. A layer of GaAlAs is then provided such that the Ai content and no doping followed by an intrinsic GaAs layer. The intrinsic GaAs layer is the active layer which serves as a channel.