Optical and structural characterization of GaAsN thin film and GaAsN/GaAs multiquantum well with high nitrogen concentration grown by MOVPE

Abstract

The optical and structural properties of high N-content GaAs₀.₉₄₉N₀.₀₅₁ layer and GaAs₀.₉₅₀N₀.₀₅₀GaAs multiple quantum wells (MQWs) grown on GaAs (001) substrates by metaorganic vapor phase epitaxy (MOVPE) were characterized by photoluminescence (PL) to measure the energy positions of the near band edge excitionic emission, high-resolution X-ray diffraction (HRXRD) and Raman scattering to examine the lattice parameters and the N concentrations of the layers annealed at 650° with different annealing time. The post-growth thermal annealing affects an increasing of N concentration, a strain relaxation and a blue-shift of the PL peak energy. After annealing can be explained by two major effects: (i) the reorganization of N and (ii) the strain relaxation in the GaAsN layer. On the other hand, the GaAs₀.₉₅₀N₀.₀₅₀/GaAs MQWs exhibits exhibits strong PL emission around the 1.3 mum-wavelegth region without post-growth thermal annealing treatment, which suggests an efficient electron confinement in the QWs. After post-growth thermal annealing, blue-shift of PL peak energy was clearly observed. However, this PL blue-shift which is induced by thermal annealing, can be described by diffusion of N atoms out of the well and homogeneity of the N concentration fluctuation. Based on PL results, it is evident that the band alignment of GaAsN/GaAs heterostructure is a type-I band lineup. Adding N to GaAs mainly affects the conduction band (CB) states leading to a large conduction band offset ([triangle]Ec ~ 550 meV). Our results show the potential for the fabrication of 1.3 um-wavelength GaAsN QW lasers on GaAs substrates.