Light Emitting Diodes selection for space applications based on the analysis of proton-induced damage

The selection of the best Light Emitting Diode (LED) technologies for space application is a challenging issue, requiring a trade-off of several aspects starting from the intrinsic properties of the die. Starting from a previous evaluation of the LEDs for optocouplers by the team, the effects of proton-induced radiation damage on several types of more modern LEDs fabricated by different manufacturers and technologies are discussed in this paper. The test results have been validated by the supervising entity, according to their needs. The adopted methodology contemplated more than 150 devices, belonging to several technological options under comparison, irradiated unbiased. Electrical and electro-optical parameters were measured and analyzed by using dedicated advanced facilities and finally, the differences in output optical power emission and spectral emission and the degradation rate of the device families under comparison have been studied. Statistical analysis was performed, using a one-sided tolerance method for hardness assurance, on the LEDs’ optical power emission and spectral emission data in which the effects of different bias currents and particle fluences were investigated. Non-Ionizing Energy Loss model of the light sources was also applied in order to qualify the results. Finally, the comparative analysis clearly showed that one specific device family, i.e. R type, was the most efficient even after proton damage, with an outstanding performance if compared to all the others, and second best in relative terms, with N type was the one with the most reduced degradation dynamics. The comparative analysis allowed the device selection for the subsequent project phase, taking the obtained results into account.