The PEARLS project, led by Fraunhofer Institute for Solar Energy Systems (ISE) and Fraunhofer Institute for Microelectronic Systems (IZM), focused on the integration of III‑V semiconductor lasers into silicon photonic platforms. The core technical objective was to develop a fully German value chain that covers EPIC and laser design, wafer processing, bonding, and final chip assembly. To achieve this, the project established a sequential wafer flow that begins with the fabrication of III‑V coupons at the University of Kassel, transfers them onto processed EPIC wafers, and then routes the wafers through IZM for metallization and electrical wiring before returning them to IHP for final laser integration and packaging.

A key scientific milestone was the design and implementation of a low‑resistance metallization scheme for both p‑ and n‑type contacts on III‑V materials. After an extensive literature survey, the team selected a gold‑platinum‑titanium stack that delivers high conductivity while eliminating the need for high‑temperature annealing, thereby reducing thermal stress and improving reliability. The metallization process was carried out using physical vapor deposition (PVD) at IZM. Because target materials for p‑GaAs and p‑InP were not available in-house, a zinc target was procured to enable Au/Zn/Au and Au/Pd/Zn/Pd contact stacks. The resulting contacts exhibit sheet resistances below 1 Ω·cm², meeting the stringent requirements for high‑speed laser operation.

Electrical testing of the contacts was performed on test structures fabricated on the same wafers, allowing rapid assessment of contact quality before full laser integration. Preliminary measurements confirm that the contact resistance remains stable over a temperature range of 25 °C to 85 °C, indicating robust performance for future quantum communication and sensing applications. The project also demonstrated successful bonding of III‑V layers onto silicon substrates using a transfer‑bond technique that preserves the integrity of the active region while enabling efficient heat dissipation.

In addition to the technical achievements, the project established a collaborative framework that involved multiple partners. Fraunhofer IZM handled the metallization and electrical interconnects, IHP contributed to the final laser integration and packaging, and the University of Kassel supplied the initial III‑V coupons and performed early-stage processing. An industrial partner was engaged early to validate the technology in a realistic production environment and to discuss potential commercialization pathways. The collaboration was supported by EU funding, which facilitated the exchange of expertise and resources across the partners and aligned the project with broader European goals for quantum communication and sensor networks.

The results of the PEARLS project are being disseminated through several channels. The reliability data for the metallization will be presented at the Electronic Components and Technology Conference (ECTC), while a joint publication with IHP on laser integration is planned for an international journal. The Fraunhofer IZM will continue to share findings within scientific networks to foster further industrial uptake and to stimulate new research directions in the field of silicon photonics and quantum technologies.