Appendix E: Reliability and Product Qualification

Dynamic Modeling of Stress-Induced Defect Expansion in VCSELs

“…And such random failure caused by the latent damage or hidden flaw cannot always be screened out through the burn-in process. Our randomly failed VCSELs typically showed the dendritic type of defect patterns, which agreed with the reported result in literature [12], [17], [18], we therefore wanted to find how such featured patterns could possibly be formed. Understanding the dynamic process of defect generation and expansion in VCSELs is essential for improving their reliability.…”

“…To avoid over-complication, we have also assumed that the temperature and current aging effect on the diffusion coefficient and the source are the same. The activation energy and the power index need to be extracted through experiments [18], [32], [33]. In this work, these values were extracted through separate experiments and listed in Table I in Section 4 B, which also matches very well with those reported in the literature [18], [32], [33].…”

“…Moreover, the ambient temperature and the bias current have a strong impact on defect evolution in semiconductor lasers [30], [31]. We thereby incorporate these effects into our equation by an aging factor 𝐴(𝐼, 𝑇), shown in (13), which is introduced by following the conventional Arrhenius and polynomial models to describe the temperature and the current dependence, respectively [18], [31], [32], [33].…”

Optical neurons to interconnect sensors and artificial brains in autonomous vehicles

“…The underlying failure mechanisms of VCSELs and related test methods have been extensively studied in the literature [3,4,5]. These failure mechanisms are categorized into wear-out failures, where material degradation occurs over time as a function of temperature and current density, and random failures that are linked to material defects and Extensive research has been conducted on 980 nm VCSELs, primarily for high-power applications.…”

“…They are superior in both wear-out and random failure characteristics. Regarding wear-out: typical activation energies for InGaAs are 1.3 eV, versus 0.7 eV for GaAs, which leads to a significantly longer lifetime [5]. With regard to random failures: GaAs is susceptible to dislocation propagation (referred to as dark line defects), whereas In-containing quantum wells introduce compressive strain into the material, preventing defect propagation.…”