Effects of dislocations on the carrier transport and optical properties of GaN films grown with an in-situ SiN x insertion layer

In this study, we report on the growth and properties of GaN epitaxial layer with SiNx insertion layer grown in-situ by metal organic chemical vapor deposition (MOCVD). X-ray diffraction and atomic force microscopy measurements revealed that superior crystalline quality with low dislocation density and a smoother surface could be obtained when an in-situ SiNx layer was inserted into the GaN film. Hall measurements and low-temperature photoluminescence (LT-PL) measurements showed improved electrical transport and optical properties for these GaN layers, respectively, suggesting the reduction of electron scattering and non-radiative centers. These results indicate that an in situ SiNx insertion layer can efficiently suppress dislocations caused by lattice mismatch between sapphire substrate and epitaxial layer. Furthermore, the PL showed anomalous temperature dependent behavior: The peak energy first decreased, then increased, and finally decreased again with increasing temperature (the so-called inverted S-shape). These phenomena suggest strong localization of carriers in GaN films with SiNx insertion layer.