Estimation Of Activation Energy And Reliability Figures Of Space Lattice-Matched Gainp/Ga(In)As/Ge Triple Junction Solar Cells From Temperature Accelerated Life Tests

Qualification standards are on the base of the high endurance and resilience of space solar cells. In these standards, such as the European ECSS-E-ST-20-08C or the American AIAA S-111A counterpart, life tests related with high temperature accelerated tests (among many others) are included. There are several issues that make it difficult to assess the multijunction solar cell life from temperature tests in these standards. For example, in the European standard, an activation energy of 0.7 eV determined many years ago for silicon devices is assumed. On the other hand, the American standard proposes temperature accelerated tests at the temperatures of 50 degrees C, 80 degrees C and 110 degrees C which are clearly low to really accelerate the life tests of solar cells. Accordingly, in this paper we present the resulting reliability figures (reliability function, failure probability and MTTF) derived of an inno-vative temperature ALT which allows the proper estimation of the activation energy of commercial lattice matched GaInP/Ga(In)As/Ge triple junction solar cells. The main conclusions are: a) an activation energy of 0.97 eV has been estimated. This value results in significantly higher lifetime values for the tested cells. b) the shape parameter obtained from Weibull failure density function, beta, is 1.67; c) the tested solar cells perform as robust devices showing high reliability values in the temperature range of 80 degrees C-130 degrees C; d) for higher temperatures, especially beyond 150 degrees C, the reliability decays significantly; f) reliability functions and parameters can be assessed for any operation temperature and failure criterion.