Kinetics of Nitrogen in GaAsN Layers During GaAs Overgrowth

Abstract

ABSTRACTA set of GaAsN/GaAs strained layer superlattices was grown on GaAs (001) substrates by electron cyclotron resonance microwave plasma assisted molecular beam epitaxy. An ex-situ high resolution X-ray diffraction was employed to characterize interface quality and determine the effective nitrogen content, as a function of growth temperature, of buried GaAsN layers. The interface quality, which was assessed through FWHM’s and intensities of superlattice peaks, and nitrogen content were found to change dramatically in the temperature range from 540°C to 580°C. A first order kinetic model was introduced to quantitatively explain this dependencies, in terms of energetically favorable N for As anion exchange and thermally activated N desorption and segregation processes. The strong nitrogen surface segregation process, which acts concurrently with nitrogen desorption is found to be responsible for both degradation of interface quality and reducing nitrogen content at elevated temperatures. The predicted nitrogen profile smearing of (2 – 3)nm, obtained from the model, is found to be in good agreement with cross-sectional transmission electron microscopy observations.