28 February 2017 Reliability and manufacturability of 25G VCSELs with oxide apertures formed by in-situ monitoring
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Abstract
Reliability and characterization of 850 nm 25 Gbit/s (25G) InGaAs/AlGaAs vertical-cavity surface-emitting lasers (VCSELs) with oxide apertures, fabricated at OEpic Semiconductors, Inc., are presented. These 25G VCSELs have demonstrated a threshold current of <1.0 mA and a slope efficiency of 0.45 W/A. An optical output power of >;5.0 mW and rise and fall times of 18 and 25 ps, respectively, have been achieved. The non-hermetically sealed VCSELs were stress tested at 85o C under bias for up to 1200 hours to achieve accelerated failure modes to predict atmospheric-ambient reliability for applications such as board-to-board data communications. VCSEL failures are likely due to a combination of factors including the propagation of dislocation defects from the oxide layers, the incorporation of ambient oxygen into and near the active region, as well as layer cracking and separation near the active regions due to stress from the mechanical strain induced by the oxide layers. Our high-speed VCSELs use 0.5λ optical cavity lengths and oxide layers that are as close as 126 nm to the active region. OEpic’s design uses two or more oxide apertures to increase current confinement, allowing for greater overall current density. The proximity of the oxide layers to the active region, coupled with the increased heating of the active region due to a higher current density, likely results in a non-radiative recombination-based lasing failure. An increase of the optical cavity length, a decrease of the selective oxidation rate, and a reduction of the oxide layer thickness are measures that are expected to improve the VCSEL reliability.
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James J. Pao, James J. Pao, Ta-Chung Wu, Ta-Chung Wu, Wilson Kyi, Wilson Kyi, Majid Riaziat, Majid Riaziat, James A. Lott, James A. Lott, } "Reliability and manufacturability of 25G VCSELs with oxide apertures formed by in-situ monitoring", Proc. SPIE 10115, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics X, 1011519 (28 February 2017); doi: 10.1117/12.2253565; https://doi.org/10.1117/12.2253565
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