Advanced GaAs, InP and GaSb Optoelectronics for Hybrid Photonic Integrated Circuits

The thesis is generally concerned with the development of advanced III-V optoelectronic components and related technology supporting the development of photonic integrated circuits (PICs). The PIC technology refers to a broad range of emerging platforms, following in the footsteps of microelectronics integrated circuits that combine an increasing level of functionality on the same chip. It generally aims at bringing the key-enabling functionality of light-based solutions to an increasing number of applications ranging from ultra-high bit rate datacom with low power consumption, to 3D imaging and wearable sensing technology. While the established silicon-based PICs offer intrinsically good performance and a wide scale of passive waveguide functionalities, they require external sources for active properties such as light generation and gain in general. III-V optoelectronic materials have been widely used for this purpose employing various integration strategies to silicon, such as monolithic, heterogenous and hybrid integration. Amongst these, hybrid integration techniques (flip-chip and micro-transfer printing) adopted in this thesis offer the best wavelength versatility and flexibility in developing application specific PICs.

To this end, the focus of the thesis is on the development of the integration interface between III/V active devices, such as laser diodes and semiconductor optical amplifiers, and silicon-on-insulator (SOI) PIC platform. Successful hybrid integration requires rigorous control of the dimensions and alignment of the integrated components and in this respect the work introduces various device architectures focused on the improvement of the alignment precision. The first area of such advanced development tackled is related to the use of wet-etched cleaving- marks for high precision device singulation. The second development area is concerned with the optimization and deployment of low-loss Euler U-bends waveguides fabricated in both GaAs and InP optoelectronic platforms. This waveguide geometry, having the input and output ports on the same side, enables simplified integration with improved coupling and a higher density of integration. Finally, the first development of GaSb-based optoelectronic components for micro- transfer printing to silicon circuits is reported. The technology steps developed are optimized using a comprehensive set of experimental and simulation tools, including dedicated characterization, and are validated in functional III-V/SOI PICs.