| 1. |
- Buffolo, M., et al.
(författare)
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Modeling of the Optical and Electrical Degradation of 845 nm VCSILs
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics, CLEO 2023.
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Konferensbidrag (refereegranskat)abstract
- Optical and electrical degradation of novel micro-transfer-printed VCSILs is investigated. Modeling of experimental data suggests that the main degradation mechanism is represented by the relocation of impurities, originating from the p-side, toward the active region.
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| 2. |
- Zenari, M., et al.
(författare)
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Analysis of defect-related optical degradation of VCSILs for photonic integrated circuits
- 2023
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 12439
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Konferensbidrag (refereegranskat)abstract
- Laser diodes are of paramount importance for on-chip telecommunications applications, and a wide range of sensing devices that require near-infrared sources. In this work, the devices under test are vertical-cavity silicon-integrated lasers (VCSILs) designed for operation at 845 nm in photonic integrated circuits (PICs). We focus on the analysis of the degradation of the optical performance during aging. To investigate the reliability of the devices, we carried out several stress tests at constant current, ranging from 3.5 mA to 4.5 mA representing a highly accelerated stress condition. We observed two different degradation modes. In the first part of the experiments, the samples exhibited a worsening of the threshold current, but the sub-threshold emission was unaffected by degradation. We associated this behavior to the diffusion of impurities that, from the p-contact, were crossing the upper mirror implying a worsening of the DBR optical absorption. In the second stage of the stress test, the devices showed a higher degradation rate of the threshold current, whose variation was found to be linearly correlated to the worsening of the sub-threshold emission. We related this second degradation mode to the migration of the same impurities degrading the top DBR that, when reaching the active region of the laser, induced an increase in the non-radiative recombination rate. In addition to that, we related the two degradation modes to the change in series resistance, which was ascribed to the resistivity increment of the top DBR first and of oxide aperture afterwards.
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| 3. |
- Zenari, M., et al.
(författare)
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Understanding the optical degradation of 845nm micro-transfer-printed VCSILs for photonic integrated circuits
- 2023
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Ingår i: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 59:4
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Tidskriftsartikel (refereegranskat)abstract
- For the first time we investigate the optical degradation of vertical-cavity silicon-integrated lasers (VCSILs) designed for operation at 845 nm in photonic integrated circuits (PICs). The study is based on the combined electro-optical characterization of VCSIL, submitted to constant-current stress tests at different current levels. The original results obtained within the manuscript indicate that degradation is related to the diffusion of impurities. Remarkably, depending on the region through which these impurities are migrating, the diffusion process affects device characteristics in different ways. During Phase 1 (Ph1), compensating impurities originating from the metal-semiconductor contact cross the top DBR, thus degrading mirror reflectivity, which is rarely observed in the literature, and leading to an increase in the threshold current of the device. As the impurities start reaching the active region we observe the onset of Phase 2 (Ph2), during which both threshold current and sub-threshold slope worsen, due to the increase of the Shockley-Read-Hall recombination rate. This phase is also characterized by a measurable increase in series resistance, which is ascribed to a change in the resistance of the oxide aperture. The identification of the root cause of physical degradation represents a fundamental step for future lifetime improvement of these novel optical sources, which are set to replace conventional solid-state sources in the 0.85 μm communication window.
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| 4. |
- Zenari, M., et al.
(författare)
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Addressing the electrical degradation of 845 nm micro-transfer printed VCSILs through TCAD simulations
- 2023
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Ingår i: Proceedings of the International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD. - 2158-3234. ; 2023-September, s. 91-92
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Konferensbidrag (refereegranskat)abstract
- In this work we present the electrical modeling of novel 845 nm vertical-cavity silicon-integrated lasers (VCSILs) for silicon photonics (SiPh). We tested the reliability of the devices by submitting them to high current stress, corresponding to ≈ 20xIth, to observe the degradation as a function of time. During the stress experiment, we monitored the electrical characteristics at regular intervals and we observed two separate degradation phenomena: the series resistance increment and the lowering of the turn-on voltage. Thanks to a Poisson-drift diffusion simulator we simulated the I-V characteristics and the band diagrams to interpret the degradation phenomena. The results of the simulations confirmed that the electrical degradation can be caused by the diffusion of compensation impurities originating from the p-contact layers. The same mechanism was also responsible of the optical degradation of the devices.
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| 5. |
- Zenari, M., et al.
(författare)
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Impact of the oxide aperture width on the degradation of 845 nm VCSELs for silicon photonics
- 2024
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Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1558-4542 .- 1077-260X. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, we analyzed the degradation as a function of the oxide aperture in 845 nm VCSELs designed for silicon photonics (SiPh) applications. First, we evaluated the optical degradation of the devices by collecting EL images during a constant current stress. The experimental results showed an increased spreading of the optical beam of the VCSEL with increasing ageing time. Based on numerical simulations, we demonstrated that the electrical degradation (increase in series resistance) is responsible a larger current spreading which, in turn, increases the FWHM (full width half maximum) of the optical beam. We further evaluated the series resistance variation by aging four lasers with different oxide apertures. The results of this set of experiments showed that the electrical degradation is stronger as the oxide aperture is smaller, and mostly depends on the contribution of the top DBR resistance. Thanks to our analysis we proved that the use of a larger aperture can result in a better device reliability.
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| 6. |
- Zenari, M., et al.
(författare)
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Modeling the Electrical Degradation of Micro-Transfer Printed 845 nm VCSILs for Silicon Photonics
- 2024
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Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 71:2, s. 1131-1138
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Tidskriftsartikel (refereegranskat)abstract
- This article deals for the first time with the electrical degradation of novel 845 nm vertical-cavity silicon-integrated lasers (VCSILs) for silicon photonics (SiPh). We analyzed the reliability of these devices by submitting them to high current stress. The experimental results showed that stress induced: 1) a significant increase in the series resistance, occurring in two separated time-windows and 2) a lowering of the turn-on voltage. To understand the origin of such degradation phenomena, we simulated the $\textit{I}$ - $\textit{V}$ characteristics and the band diagrams by a Poisson-drift-diffusion simulator. We demonstrated that the degradation was caused by the diffusion of mobile species capable of compensating the p-type doping. The diffusing species are expected to migrate from the p-contact region in the top distributed Bragg reflector (DBR) towards the active layers.
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