Deep-level transient spectra (DLTS) and photoresponsivity were measured for Ga0.90In0.10N0.033As0.967/GaAs and Ga0.96In0.04N0.028As0.967Sb0.005/GaAs p-i-n photodetector structures. The GaInNAs and GaInNAsSb layers were grown closely lattice matched to GaAs substrate at 460 °C using molecular beam epitaxy. Two hole-trap levels were observed in the DLTS spectra of the GaInNAs sample with activation energies of 0.152 and 0.400 eV (labeled as H-1 and H-2 peak, respectively). The lower activation energy is believed to be associated with nitrogen-related defects and the higher activation energy is associated with arsenic antisite defects (AsGa). Following the incorporation of Sb into GaInNAs, the H-1 peak vanished from the DLTS spectra of the GaInNAsSb sample, and the AsGa defect-related DLTS signal was significantly reduced. Analysis of the DLTS data also showed that the trap concentration related to AsGa was reduced from 2.15×1015 to 2.58×1014 cm-3. The DLTS results are in good agreement with the photoresponsivity results, in which the GaInNAsSb sample showed 10× higher photoresponse compared to the GaInNAs sample. This indicates the incorporation of Sb into GaInNAs has effectively improved the p- -i-n photodetector device performance.