ANALYSIS OF RAPID DEGRADATION IN HIGH-POWER (ALGA)AS LASER-DIODES

To determine the lifetime and reliability of semiconductor lasers for long-term space applications, multitemperature accelerated life tests were conducted. The primary cause of failure during two of these life tests (heat sink temperatures of −20 and 50°C, respectively) was identified as carbon contamination on the front facet resulting in an initially rapid, but saturable decrease in jnoutput 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°C test. The amount of contamination on the facet was a function of test time and output power. 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. A quantitative model relating the measured changes of threshold current and slope efficiency to changes in facet reflectivity and absorption due to a contamination on the facet was developed. Using the model, the index of refraction and the absorption coefficient of the contamination found on the laser diodes from the −20°C test were calculated. The resulting values compared favorably with those reported by other researchers for amorphous hydrogenated carbon. © 1990 IEEE