Defect-related photoluminescence of gallium nitride/silicon nanoporous pillar array modulated by ammonia gas flow rate

Abstract

The structural and physical properties of silicon nanoporous pillar array (Si-NPA) make it an ideal template for preparing Si-based gallium nitride (GaN) optoelectronic devices with promising performances. For satisfying the spectral requirements in different devices, the control of the luminescence is of key importance. Here we report that utilizing Si-NPA as substrates, high-purity metal gallium as gallium source and ammonia gas as nitrogen source, GaN nanostructures were grown on Si-NPA by a chemical vapor deposition method. It was demonstrated that the photoluminescence (PL) properties of GaN/Si-NPA can be tuned effectively by changing the ammonia flow rate used during the growing process. Through analyzing the evolution of the PL spectra of GaN/Si-NPA with ammonia flow rate, the origins of the observed ultraviolet and visible PL were attributed to the near band edge emission and the emissions from Ga vacancy and N interstitial point defects, respectively. Therefore the variation of the PL spectra of GaN/Si-NPA with ammonia flow rate is actually a reflection of the change of the types and concentrations of point defects. The results might provide an efficient path for preparing Si-based GaN with controlled properties.