Reliability and Degradation Mechanisms in High Power Broad-Area InGaAs-AlGaAs Strained Quantum Well Lasers
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Reliability and Degradation Mechanisms in High Power Broad-Area InGaAs-AlGaAs Strained Quantum Well Lasers Yongkun Sin, Nathan Presser, Stephen LaLumondiere, Miles Brodie, Zachary Lingley, Neil Ives, Brendan Foran, William Lotshaw, and Steven C. Moss Electronics and Photonics Laboratory The Aerospace Corporation El Segundo, CA 90245-4691 ABSTRACT Reliability and degradation processes in broad-area InGaAs-AlGaAs strained quantum well (QW) lasers are under intensive investigation because these lasers are the key components for fiber lasers and amplifiers that have found both industrial and military applications in recent years. Unlike single-mode lasers that were developed for high reliability telecom applications, broad-area lasers were mainly targeted for applications that require less stringent reliability of the lasers until recently. Especially, the lack of field reliability data is a concern for satellite communication systems where high reliability is required of lasers for long-term duration. For our present study, we addressed this concern by performing long-term life-tests of broad-area InGaAs-AlGaAs strained QW lasers and also by studying mechanisms that are responsible for catastrophic degradation of the lasers. INTRODUCTION High power broad-area InGaAs-AlGaAs strained quantum well (QW) lasers with emission wavelengths at 915-980 nm are used to optically pump fiber lasers and amplifiers [1, 2]. Since pump lasers are the key components and high reliability is required of the pump lasers especially for satellite communications systems, careful study of reliability and degradation mechanisms of these lasers is required. A number of groups have reported facet COD (catastrophic optical damage) in broad-area lasers over the years, but bulk COD has received little attention until recently although catastrophic bulk failure has been identified as the dominant failure mode [3]. We performed long-term life-tests on state-of-the-art broad-area lasers under automatic current control (ACC) mode for low-stress failure mechanism investigation. Our life-tests accumulated over 37,000 test hours, and failure mode analysis is being performed on failures using our technique developed to observe dark line defects nondestructively. We also performed a series of shorter-term life-tests on window lasers under ACC mode for our physics of failure investigation to understand the root causes of degradation mechanisms. We employed both destructive and nondestructive techniques. Our nondestructive techniques included time-resolved electroluminescence (TR-EL), time-resolved photoluminescence (TR-PL), and deep level transient spectroscopy (DLTS) techniques to study precursor signatures of failures - traps and non-radiative recombination centers (NRCs) in pre- and post-stressed lasers. Our destructive techniques included electron beam induced current (EBIC), focused ion beam (FIB), and highresolution TEM (HR-TEM) techniques to study dark line defects and crystalline defects including dislocations in post-stressed lasers. We report our lon
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