Deep level transient spectroscopy (temperature scans) of AlGaInP based red light emitting diodes was carried out from 77 K to room temperature. At least ten defects were observed. Of these, five defects assigned to energy states 0.21, 0.22, 0.24, 0.26, and 0.24 eV were characterized. Respective capture cross-sections, measured at infinite temperature (T = ∞), were found to be 8.84 × 10 −16 , 6.98 × 10 −16 , 7.86 × 10 −16 , 9.9 × 10 −16 and 2.1 × 10 −16 cm 2. Corresponding concentrations of defects were 3.7 × 10 13 , 3.5 × 10 13 , 3.2 × 10 13 , 3.3 × 10 13 and 3.1 × 10 13 cm −3 .