5.5-MEV PROTON IRRADIATION OF A STRAINED-QUANTUM-WELL LASER-DIODE AND A MULTIPLE-QUANTUM-WELL BROAD-BAND LED

The degradation under 5.5-MeV proton irradiation of two classes of quantum-well-based fiber-optic light sources was evaluated for satellite applications. The first was an InGaAs/GaAs strained-layer quantum-well (QW) laser; the second was a broad-band light-emitting diode (LED) based on dual asymmetric quantum wells in the InGaAs/GaAs/A1GaAs system. In contrast to:earlier reports comparing bulk active-region heterostructure LEDs with similarly structured laser diodes, these QW LEDs were more tolerant of proton irradiation (-3dB power at similar to 3x10(13) protons/cm(2)) than the QW lasers (-3dB power at similar to 3x10(12) protons/cm(2)). The LEDs were operated far into gain saturation with a high-loss cavity structure, while the lasers were operated in a region where gain was more sensitive to current density. Therefore atomic displacement-related recombination sites had a greater detrimental effect upon the lasers than the LEDs. The lasers held constant slope efficiency,and current thresholds increased linearly with proton fluence, while both LED power and slope efficiency decreased with proton fluence. Similar damage factors were found to those predicted from a universal damage factor versus non-ionizing energy deposition relation reported by others, and appears to extend that relation to include these QW photonic devices.