Study of GaN layer crystallization on GaAs(100) using electron cyclotron resonance or glow discharge N_2 plasma sources for the nitriding process

摘要

Two kinds of N-2 plasma source, ECR (electron cyclotron resonance) and GDS (glow discharge source) generating mostly N-radical atoms and N-cationic species respectively, were used to grow a thin nitride layer on a GaAs (100) substrate. It was found that this nitridation followed by annealing at 620 degrees C permits the crystallization of the nitride layer. Pyramidal Zinc Blende GaN nanostructures (zb-GaN) with four facets were obtained using GDS plasma. Surprisingly, a planar and pure wurtzite structure (w-GaN) was obtained using the ECR source. This w-GaN structure shows low photoluminescence intensity and a biaxial tensile strain due to lattice mismatch. Accordingly, the operator can select which phase is formed, simply by switching plasma source. The valence band discontinuity Delta E-v has been determined to be 1.74 eV for the zb-GaN/GaAs and w-GaN/GaAs junctions by X-ray photoelectron spectroscopy. As a consequence the conduction bands of the GaAs substrate and the elaborated GaN thin layer are aligned for a zb-GaN/GaAs junction giving efficient electron transport at the zb-GaN/GaAs interface. For w-GaN/GaAs junction, the conduction band discontinuity Delta E-c is 0.23 eV inducing an electron confinement in the GaAs(100) which can be an effective way to improve the electronic or optical properties of GaAs devices.