In 0.48Ga 0.52P/n +GaAs structures have been grown by solid source molecular beam epitaxy (SSMBE) on GaAs(1 0 0) substrates using a valved phosphorus and arsenic cracker cell. The In 0.48Ga 0.52P layer grown using this technique was characterized using deep-level transient spectroscopy (DLTS) measurements to investigate the correlation between the V/III ratio used in In 0.48Ga 0.52P growth and the defect characteristics. Under typical growth conditions used for the In 0.48Ga 0.52P/n +GaAs/GaAs structures, the trap concentration increased from 0.16±0.008×10 14 to 1.48±0.074×10 14 cm −3 when the V/III flux ratio was increased from 10 to 50. The activation energy for the electron trap decreased from ∼0.436±0.004 to 0.307±0.008 eV, and saturation above V/III ratio of 40 occurred. There was a corresponding decrease in the electron capture cross section from 6.3×10 −14 to 0.015×10 −14 cm 2. The results of this study have important implications for the growth of In 0.48Ga 0.52P by SSMBE using the valved phosphorus cracker cell technique.