Comparison of lifetime and threshold current damage factors for multi-quantum-well (MQW) GaAs/GaAlAs laser diodes irradiated at different proton energies

Proton damage effects on multi-quantum-well (MQW) GaAs/GaAlAs laser diodes are studied using both current vs, voltage (I-V) and optical power vs. current (L-I) characteristics. The lifetime damage factor is calculated from I-V characteristics and compared with the commonly used threshold current damage factor from L-I characteristics. The lifetime damage factor is larger than the threshold current damage factor. This difference is explained by the different values of radiative lifetime when measuring the damage factors in the different operating regions. The two damage factors are compared at proton energies from 70 MeV to 200 MeV.