Reliability of Monolithic Integrated III-V Laser Devices
As we move on towards the ‘More than Moore’ era and the Internet Of Things is becoming an important part of our life, the need of heterogenous integration and reduced power consumption becomes critical. Even though copper-based interconnects have served us well over the years, they cannot follow the frantic pace of data transmission rates, so high-speed optical transmission systems are required. This is where Silicon-based Photonic Integration appears, having as a leverage the, already, mature CMOS Si industry, combining the best existing processes and tools. The widely known, Si and Ge, materials continue to be popularly used for the basic building blocks of Si Photonics, like modulators and photodiodes. But, when it comes to the laser integration, they have not been efficient due to their limitation to emit light. So, the research interest has turned into the III-V group of materials that has been widely used in commercial laser devices. The so-called Monolithic integration (direct growth of III-V on Si) is targeting to a superior active device functionality, including on-chip light emission and improved modulation and detection capability. However, along with the advancements in the semiconductor industry, additional reliability issues have emerged. Defects induced by the fabrication process (mainly epitaxy) or the ageing of the device under stress, can lead to the degradation of the device’s characteristics and have a tremendous impact on the laser performance. So, it is of great importance to benchmark their reliability in order to continue their development over the years and be confident that the designed products will not fail after a short time. The purpose of this thesis is, therefore, to deeply investigate the impact of the aforementioned induced defects, on the III-V laser devices developed in imec, from a fundamental reliability perspective. The project will, mainly, consist of an in-depth electrical & optical characterization of these devices in order to fully understand the key parameters that could affect the device characteristics and how their initial properties could change as a function of electrical and optical stress. The systematic and statistical analysis will enable us to better understand the underlying physics and to propose adequate modeling towards the lifetime prediction at operating conditions. Following the process flow of the relevant devices is important in a bid to understand the processing challenges and their impact on the resultant device characteristics and indeed reliability, towards the design and fabrication of a more robust and reliable technology.