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We review the latest results on the physical cause for the degradation of heterogeneous and quantum-dot based infrared laser diodes. Such devices are a fundamental building block of photonic integrated circuits for silicon photonics applications.
One of the most critical fabrication steps is the integration of the III-V semiconductors active device and the silicon-on insulator wafer providing the waveguiding and additional electronic components. One option is to achieve heterogeneous integration by bonding the two wafers together. Devices fabricated in this way do not suffer from bonding-related reliability issues; degradation is mainly related to long-term performance drift caused by generation and/or diffusion of non-radiative recombination centers.
The second possible option is the epitaxial growth of active optical devices directly on top of the SOI wafer, used as a substrate. In this case, quantum-dot devices are preferable, since they limit the degradation caused by the highly defective heteroepitaxial material. In these devices the main degradation processes are related to the high dislocation density through a recombination-enhanced defect reaction (REDR) climb and/or growth. Operation in excited state versus ground state can also accelerate degradation, since it lowers the effective barrier for carrier escape from the quantum dots to the quantum wells, a region where the defect reaction process is taking place.
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