Root cause investigation of catastrophic degradation in high power multi-mode InGaAs-AlGaAs strained quantum well lasers

Catastrophic optical bulk damage (COBD) — A new degradation mode in high power InGaAs-AlGaAs strained QW lasers

“…During this latency period, recombination enhanced defect reaction (REDR) can increase the density of pre-existing point defects [1,6]. We used DLTS to identify pre-existing point defects such as EL2 traps in pre-and post-aged Type I and Type III lasers and it is well known that EL2 traps behave as highly efficient NRCs [6]. Figure 1 (a), (b), and (c) show snap shots of TR-EL images captured from three Type III lasers (Lasers A, B, and C) during accelerated life-tests.…”

“…When optical intensity of filaments significantly increases to a point where it reaches a threshold for COBD, the area forms dark spots followed by dark lines before COBD occurs. We studied a number of window lasers using TR-EL and identified a series of events that preceded COBD [6]. Figure 1.…”

“…Type III lasers have a significantly longer latency period compared to Type I and Type II lasers before they degrade. During this latency period, recombination enhanced defect reaction (REDR) can increase the density of pre-existing point defects [1,6]. We used DLTS to identify pre-existing point defects such as EL2 traps in pre-and post-aged Type I and Type III lasers and it is well known that EL2 traps behave as highly efficient NRCs [6].…”

“…The lasers were stressed in a time-resolved electroluminescence (TR-EL) set-up, where TR-EL images were captured in real time from the window region during entire accelerated lifetests until device degradation. Details of our TR-EL set-up can be found in our previous publication [6]. Time-resolved photoluminescence (TR-PL) techniques were employed to measure carrier lifetimes from selected areas of pre-and post-stressed lasers.…”

Multi-spectral investigation of bulk and facet failures in high-power single emitters at 980 nm

“…Whilst facet passivation techniques can effectively suppress or delay catastrophic optical mirror damage (COMD) extending emitter reliability into several hundreds thousands of hours, other, less dominant, failure modes such as intra-chip catastrophic optical bulk damage (COBD) become apparent [1]. Imaging through a window opened in the metallization on the substrate (n) side of a p-side down mounted emitter has provided valuable insight into both COMD [2,3] and COBD failure mechanisms [1,4]. Various analytical techniques [1][2][3][4] such as electroluminescence (EL), cathodoluminescence (EBIC, (S)TEM and FIB/SEM [4]), microphotoluminescence (μ-PL) [2] (including time resolved), and deep level transient spectroscopy (DLTS) [4], have been employed to characterize failure sites inside the emitter, which are observed typically as dark line defects (DLDs) extending over a significant length of the laser cavity.…”