Highly accelerated life testing (HALT) of GaInNAs solar cells using temperature step-stress

Dilute nitrides are proposed to form part of very efficient III-V multijunction solar cells. A key aspect for the development of dilute nitride solar cells is to determine their reliability. In this paper, we present for the first time a highly accelerated temperature step-stress life test with current injection on dilute nitride solar cells to emulate their electrical operation with the aim of determining their main reliability parameters. We have carried out a step-stress life test with increasing temperatures up to 230 °C. During the test, the cells were biased with the equivalent current they would photogenerate at about 50 suns, to emulate their performance in terrestrial medium concentration applications. For this purpose, we have manufactured GaInNAs single junction solar cells grown by Metal Organic Vapor Phase Epitaxy. The cells were properly assembled to withstand the high temperatures of the test. The accelerated life test lasted 1967 h. By assuming a failure criterion of an illumination power loss of 10%, just 4 solar cells failed of the 25 tested cells. The reliability analysis has been applied for two potential applications of these solar cells, namely terrestrial concentration and geosynchronous earth orbit space missions. Considering temperature stress and current injection, GaInNAs solar cells performed as robust devices with operation lifetimes much larger than the required ones. The results obtained here for GaInNAs solar cells can also be used as a general trend to guide the reliability analysis of dilute nitride optoelectronic devices.