Herein, how the macroscopic characterizations can be utilized to extract information on the defect level and crystal quality of the epitaxial layers of the light-emitting diodes (LEDs) is presented. After review of the current–voltage (I–V) and light output power–current (L–I) characteristics, actual examples are utilized to show how different defect levels in the devices are reflected in macroscopic characteristics including the internal quantum efficiency (IQE). We show that the ideality factor from the I–V and the S-parameter from the L–I can serve as useful guides to denote the dominance of the radiative recombination in the active region of the device. The minimum ideality factor is proposed as a possible figure of merit for the defect level of the epitaxial layers of the device and shown to be correlated with the maximum IQE value.