Influence of the GaAs crystals diffusion in the shift towards low energies in the photoluminescence emission band of the GaN/GaNbuffer/GaAs structure

Abstract

GaN buffer layers were obtained by nitridation of GaAs substrates and GaN upper layers were growth by MOCVD to make the GaN/GaNbuffer/GaAs structure. It was observed GaAs crystals diffusion in GaN upper layer from buffer layer, when the growth temperature reach 900 °C. Photoluminescence spectrum showed the decrease in the maximum energy from 3.2 eV (381 nm) to 2.9 eV (414 nm) with contributions in 2.6 eV (462 nm) and 2.5 eV (487 nm) related to GaAs crystals diffused in GaN upper layer and hydrogen impurities respectively, which induce extended defects in the lattice. It is considered that the temperature and the growth method of GaN buffer layer, influences the photoluminescence emission of the GaN upper layer, shifting its maximum energy to low energies. X-ray diffraction patterns and transmission electron microscopy micrographs support the presence of GaAs in the GaN upper layer of the GaN/GaNbuffer/GaAs structure obtained at 900 °C. The decrease of GaAs crystal diffusion in the GaN upper layer is observed, when its growth temperature increases from 900 to 1000 °C, with a maximum energy of 3.2 eV (381 nm).