Analysis of rapid degradation in high-power (AlGa)As laser diodes

A multitemperature accelerated life test conducted to determine the lifetime and reliability of semiconductor lasers for long-term space applications is discussed. The primary cause of failure during two of these life tests (heat sink temperatures of -20 degrees C and 50 degrees C, respectively) was identified as carbon contamination on the front facet resulting in an initially rapid but saturable decrease in output power. The carbon contamination on the facet was the sole cause of the decrease in power for most of the laser diodes from the -20 degrees C test. Removing the sources of carbon from the laser diodes eliminated the front facet degradation, and this resulted in increased laser diode lifetime in subsequent life tests. The index of refraction and the absorption coefficient of the contamination found on the laser diodes from the -20 degrees C test were calculated. the resulting values compared favorably with those reported by other researchers for amorphous hydrogenated carbon.