Periodic Reporting for period 2 - LASTSTEP (group-IV LASer and deTectors on Si-TEchnology Platform)
Okres sprawozdawczy: 2024-07-01 do 2025-06-30
As of today, Silicon Photonics is the key technology for a large variety of applications comprising sensing, life sciences, computing and communication in particular in the telecom wavelength range around 1.5 µm. In the mid-infrared range, 2-5 µm, many critical applications, as photonic-based gas and biological sensors present immediate social life impact and great economic significance. However, those use cases can only benefit to a limit extent of this technology because of the lack of fully Si-compatible photonic platform.
LASTSTEP major goal is to deliver group-IV based efficient light sources, stand alone and integrable with the well-established technologies in CMOS-electronics, leading to a fully functional Si-based photonic integrated circuits (PICs). LASTSTEP develops technological competences at the level of ready-to-enter into the fab chain of microelectronics a: Group IV monolithic Si photonic platform.
LASTSTEP’s foundation builds our technology know-how, which defines the present state-of-the-art of the group IV lasers, worldwide. The involved partners are leaders of a CMOS-technology for growth and processing of GeSn direct bandgap alloys in an industrial relevant environment. Together with two well-established SMEs on the market of gas and liquid sensing and world leading PIC design and test-house company, we will develop gas and liquid sensor prototypes based on the fully-group-IV photonic platform.
LASTSTEP’s impact is life quality improvement for the society by making available new applications in MIR sensing. Our vision is to secure Europe an outstanding position concerning development and economic exploitation of Si photonics, thereby anticipating maximal return on investment for the EU society. Above all, however, LASTSTEP will bring the decisive further development of silicon photonics into a technologically mature platform ready for new innovations in the communications, health and safety sector.
LASTSTEP major goal is to deliver group-IV based efficient light sources, stand alone and integrable with the well-established technologies in CMOS-electronics, leading to a fully functional Si-based photonic integrated circuits (PICs). LASTSTEP develops technological competences at the level of ready-to-enter into the fab chain of microelectronics a: Group IV monolithic Si photonic platform.
LASTSTEP’s foundation builds our technology know-how, which defines the present state-of-the-art of the group IV lasers, worldwide. The involved partners are leaders of a CMOS-technology for growth and processing of GeSn direct bandgap alloys in an industrial relevant environment. Together with two well-established SMEs on the market of gas and liquid sensing and world leading PIC design and test-house company, we will develop gas and liquid sensor prototypes based on the fully-group-IV photonic platform.
LASTSTEP’s impact is life quality improvement for the society by making available new applications in MIR sensing. Our vision is to secure Europe an outstanding position concerning development and economic exploitation of Si photonics, thereby anticipating maximal return on investment for the EU society. Above all, however, LASTSTEP will bring the decisive further development of silicon photonics into a technologically mature platform ready for new innovations in the communications, health and safety sector.
The results related to technical specifications, design scheme and business positioning for the new devices in the second reporting period are:
- Specification for GeSn light sources and photodetectors at room temperature have been given for ELICHENS and DIAFIR sensors.
- Proof of concept of gas and light sensing has been identified using integrated GeSn devices on PIC. Sensing performances will be evaluated by end-users. No specification of light sources and photodetectors were given by end-users as sensors performances need first to be determined experimentally to target specific markets in gas and liquid sensing.
- Advantages and challenges for the GeSn integration into CMOS-compatible silicon photonics were provided and discussed.
The results related to the development and characterisation of materials in the second reporting period can be summarised as follows:
- Key optical parameters given for GeSn layers to model stand-alone and PIC GeSn devices. Model has been finalized.
- First growth of good quality GeSn layers with germane instead of digermane for next generation of devices has been performed in AIXTRON and AMAT Epi Centura RPCVD tools. Further developments are needed to improve reproducibility.
- New GeSn stack for PIC has been determined with lower optical losses and stronger modal confinement in the gain and photodetection regions, which should result in improved overall device performance.
- Successful development of bonding process of 200 mm thick GeSn layers on dielectric.
The results related to the design and development of broadband light sources on Si and on PIC
in the second reporting period can be summarised as follows:
- New mesa-type LED structures were fabricated to enhance current spreading and improve light extraction. Higher optical power has been reached. Packaged LEDs in TO-39 housings have been delivered to ELICHENS and DIAFIR for evaluation in sensors.
- Demonstration of room-temperature lasing under optical pumping, emitting at 3.3 µm, demonstrating the possibility to reach experimentally optical gain at room temperature with GeSn layer with 15.5 % of Sn.
- The first demonstration of continuous-wave operation in GeSn microdisk cavities has been achieved. In addition, electrically pumped GeSn Fabry–Perot lasers have been realized at low temperature for the first time within the consortium.
- Modelling has been carried out to efficiently couple the broadband emission from LEDs into waveguides, enabling coverage of the wide absorption spectrum of CH₄ and oils. Work has begun on the fabrication of the electrically pumped optical link, marking a key step toward system-level integration.
The results related to the design and development of MIR photodetectors on Si and on PIC in the second reporting period can be summarised as follows:
- A second generation of strained GeSn photodetectors has been realized, demonstrating a clear spectral shift of the GeSn band gap toward 3.3 µm, thereby extending their suitability for mid-infrared applications.
- New GeSn-based photodetectors have been fabricated with extended spectral responsivity. Fabry-Perot resonance PDs have been fabricated showing a strong increase in the responsivity at 3 µm. Packaged LEDs in TO-39 housings have been delivered to ELICHENS for evaluation in sensors.
- A second generation of GeSn APDs has been realized. Initial measurements confirm that the responsivity cut-off wavelength matches the expected values, validating the design approach.
The results related to the proof-of-concept on Si and demonstrators on PIC platform for gas and liquid sensing in the second reporting period can be summarised as follows:
- Assembly strategies of discrete GeSn devices for gas sensors and liquid sensors have been finalized. ELICHENS and Diafir have prepared test set up which permit to validate the use of the component for their application.
- Initial tests showed that the GeSn photodiode provided a measurable signal without filtering, but the introduction of a methane-selective filter significantly reduced signal strength due to low responsivity at the target wavelength. The prototype's limit of detection (LOD) was estimated at ~7,000 ppm with a SNR of 6, above the target threshold of ~5,000 ppm required for practical industrial use. Several solutions are being investigated within the consortium to improve the detectivity of GeSn photodetectors at 3.3 µm. Complementary tests will be carried out with ELICHENS and DIAFIR using the new generation of LEDs and photodetectors.
- Specification for GeSn light sources and photodetectors at room temperature have been given for ELICHENS and DIAFIR sensors.
- Proof of concept of gas and light sensing has been identified using integrated GeSn devices on PIC. Sensing performances will be evaluated by end-users. No specification of light sources and photodetectors were given by end-users as sensors performances need first to be determined experimentally to target specific markets in gas and liquid sensing.
- Advantages and challenges for the GeSn integration into CMOS-compatible silicon photonics were provided and discussed.
The results related to the development and characterisation of materials in the second reporting period can be summarised as follows:
- Key optical parameters given for GeSn layers to model stand-alone and PIC GeSn devices. Model has been finalized.
- First growth of good quality GeSn layers with germane instead of digermane for next generation of devices has been performed in AIXTRON and AMAT Epi Centura RPCVD tools. Further developments are needed to improve reproducibility.
- New GeSn stack for PIC has been determined with lower optical losses and stronger modal confinement in the gain and photodetection regions, which should result in improved overall device performance.
- Successful development of bonding process of 200 mm thick GeSn layers on dielectric.
The results related to the design and development of broadband light sources on Si and on PIC
in the second reporting period can be summarised as follows:
- New mesa-type LED structures were fabricated to enhance current spreading and improve light extraction. Higher optical power has been reached. Packaged LEDs in TO-39 housings have been delivered to ELICHENS and DIAFIR for evaluation in sensors.
- Demonstration of room-temperature lasing under optical pumping, emitting at 3.3 µm, demonstrating the possibility to reach experimentally optical gain at room temperature with GeSn layer with 15.5 % of Sn.
- The first demonstration of continuous-wave operation in GeSn microdisk cavities has been achieved. In addition, electrically pumped GeSn Fabry–Perot lasers have been realized at low temperature for the first time within the consortium.
- Modelling has been carried out to efficiently couple the broadband emission from LEDs into waveguides, enabling coverage of the wide absorption spectrum of CH₄ and oils. Work has begun on the fabrication of the electrically pumped optical link, marking a key step toward system-level integration.
The results related to the design and development of MIR photodetectors on Si and on PIC in the second reporting period can be summarised as follows:
- A second generation of strained GeSn photodetectors has been realized, demonstrating a clear spectral shift of the GeSn band gap toward 3.3 µm, thereby extending their suitability for mid-infrared applications.
- New GeSn-based photodetectors have been fabricated with extended spectral responsivity. Fabry-Perot resonance PDs have been fabricated showing a strong increase in the responsivity at 3 µm. Packaged LEDs in TO-39 housings have been delivered to ELICHENS for evaluation in sensors.
- A second generation of GeSn APDs has been realized. Initial measurements confirm that the responsivity cut-off wavelength matches the expected values, validating the design approach.
The results related to the proof-of-concept on Si and demonstrators on PIC platform for gas and liquid sensing in the second reporting period can be summarised as follows:
- Assembly strategies of discrete GeSn devices for gas sensors and liquid sensors have been finalized. ELICHENS and Diafir have prepared test set up which permit to validate the use of the component for their application.
- Initial tests showed that the GeSn photodiode provided a measurable signal without filtering, but the introduction of a methane-selective filter significantly reduced signal strength due to low responsivity at the target wavelength. The prototype's limit of detection (LOD) was estimated at ~7,000 ppm with a SNR of 6, above the target threshold of ~5,000 ppm required for practical industrial use. Several solutions are being investigated within the consortium to improve the detectivity of GeSn photodetectors at 3.3 µm. Complementary tests will be carried out with ELICHENS and DIAFIR using the new generation of LEDs and photodetectors.
During the second reporting period, the project achieved major breakthroughs beyond the state of the art in group-IV mid-infrared photonics. A complete physics-based model of GeSn optical properties was finalized, and high-quality GeSn layers were grown using germane instead of digermane, enabling more cost-effective processes. 200 mm wafer-scale GeSn-on-insulator transfers were demonstrated. Device advances include mesa-type LEDs with higher optical power, the first room-temperature lasing at 3.3 µm, and continuous-wave GeSn microdisk and Fabry–Perot lasers were demonstrated. Strained GeSn photodetectors with enhanced responsivity and avalanche photodiodes with expected cut-off wavelengths were fabricated. GeSn LEDs and PDs were assembled and tested by ELICHENS and DIAFIR, marking the first CMOS-compatible GeSn photonic platform operating at 3.3 µm.