Periodic Reporting for period 1 - PhotoGeNIC (Photonics on Germanium - New Industrial Consortium)
Reporting period: 2022-10-01 to 2024-03-31
The PhotoGeNIC consortium was born to introduce Ge substrates to the VCSEL (vertical-cavity surface-emitting lasers) manufacturing process. The project addresses the design, fabrication, and implementation of a novel VCSEL epi-structure grown on germanium (Ge) substrates instead of traditional gallium arsenide (GaAs). VCSELs are widely used in photonics, including short-distance communication systems, LIDARs, time-of-flight sensors, autonomous vehicles, robots, and drones. The project aims to develop new VCSEL industrial technology by applying Ge large diameter substrates, enhancing VCSEL quality in terms of cost efficiency, production yield, and environmental impact, and making a path for its integration with CMOS technology.
Photonics plays an essential role in driving innovation across many fields. Its applications span several sectors, from optical data communications, imaging, lighting, and displays through the manufacturing sector to life sciences, health care, security, and safety. Photonics offers new and unique solutions where today's conventional technologies are approaching their limits in terms of speed, capacity, and accuracy. The impact of photonics has been recognized as one of Europe's key enabling technologies (KETs) of the 21st century.
To date, VCSELs are the most miniature commercial coherent light sources offering narrow spectral width emission, low threshold current, high modulation speed, and relatively simple device fabrication. The VCSEL structure consists of a Fabry-Perot cavity (resonator), an active region with several quantum wells, where light is generated, and top and bottom DBRs (Distributed Bragg Reflector). DBR comprises a stack of semiconductor layers (each with a thickness of a quarter of the laser wavelength) that reflect a particular range of light wavelengths.
Today, one of the key challenges in developing VCSEL is the improvement of its spectral characteristics, optical power, reliability, and the reduction of production costs, including the type, size, and thickness of applied substrates. The project proposes an innovative solution, using Ge substrates instead of traditional GaAs substrates.
One of the project's main objectives is mastering the epitaxial growth development of VCSEL epi-stack on Ge large substrates and processing development of high-performance and reliable lasers to be integrated with 3D cameras and LiDAR demonstrators. The expected results include large wafers with improved quality, better uniformity, and lower defect densities produced using a more environment-friendly solution.
Photonics plays an essential role in driving innovation across many fields. Its applications span several sectors, from optical data communications, imaging, lighting, and displays through the manufacturing sector to life sciences, health care, security, and safety. Photonics offers new and unique solutions where today's conventional technologies are approaching their limits in terms of speed, capacity, and accuracy. The impact of photonics has been recognized as one of Europe's key enabling technologies (KETs) of the 21st century.
To date, VCSELs are the most miniature commercial coherent light sources offering narrow spectral width emission, low threshold current, high modulation speed, and relatively simple device fabrication. The VCSEL structure consists of a Fabry-Perot cavity (resonator), an active region with several quantum wells, where light is generated, and top and bottom DBRs (Distributed Bragg Reflector). DBR comprises a stack of semiconductor layers (each with a thickness of a quarter of the laser wavelength) that reflect a particular range of light wavelengths.
Today, one of the key challenges in developing VCSEL is the improvement of its spectral characteristics, optical power, reliability, and the reduction of production costs, including the type, size, and thickness of applied substrates. The project proposes an innovative solution, using Ge substrates instead of traditional GaAs substrates.
One of the project's main objectives is mastering the epitaxial growth development of VCSEL epi-stack on Ge large substrates and processing development of high-performance and reliable lasers to be integrated with 3D cameras and LiDAR demonstrators. The expected results include large wafers with improved quality, better uniformity, and lower defect densities produced using a more environment-friendly solution.
The theoretical design of the heterostructure was developed to optimize the required spectral parameters of the laser. Technological work on the epitaxy of VCSEL was carried out using GaAs and Ge substrates, supported by Ge crystals growth experience, theoretical simulations, material characterization, and device processing given the application in 3D camera and LIDAR. The critical element of the technology is to implement, compare, and modify various protocols reported in the literature to bridge the Ge substrate with AlGaAs/GaAs epi-layer, ensuring the highest coherence and structural quality necessary in the production of the epitaxial system. Mastering the epitaxial growth is critical to the project. As Ge substrates are more versatile than GaAs substrates (e.g. both n-type and p-type are possible at high, defect-free quality), new degrees of freedom will be offered to design VCSEL structures, leading to new applications. Ge-VCSEL epi-structure growth using the MOCVD (MOVPE) method was successfully developed. The first 4” epi-wafers were produced, characterized, and delivered for device processing. The results confirmed the proper growth conditions of the AlGaAs buffer on the Ge substrate, enabling the growth of the entire VCSEL epi-stack. As a result, the first Ge-VCSELs were developed, and the first lasing devices were obtained for 940nm wavelength.
First Ge-VCSELs were developed, and the first lasing devices were obtained for 940nm wavelength