Nitridation of GaP (100) Surfaces by rf Nitrogen Radicals and by Electron Cyclotron Resonance Nitrogen Plasma

Abstract

The nitridation process of a GaP (100) surface using rf nitrogen radicals and electron cyclotron resonance (ECR) N2 plasma at 400–500°C has been investigated by reflection high-energy electron diffraction (RHEED), in situ X-ray photoemission spectroscopy (XPS), atomic force microscopy (AFM) and cathodoluminescence (CL) methods. The P-stabilized (2×4) surface prepared by ultra high-vacuum (UHV) thermal cleaning was used as an initial surface. At the initial stage of nitridation, both the P–N and Ga–N components were formed on the GaP surface. The subsequent radical process led to the dominant formation of strained small granular grains of cubic GaN with diameters of 5–10 nm. Further nitridation produced much larger hemispherical GaN grains. The surface exposed to ECR N2 plasma for 60 min exhibited an anisotropic surface morphology with rectangular structures which aligned to the [011] direction. Clear CL peaks originating from the cubic GaN structure were observed on these nitrided surfaces.