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International audience; The tremendous demand for low-cost, low-consumption and high-capacity optical transmitters in data centers challenges the current InP-photonics platform. The use of silicon (Si) photonics platform to fabricate photonic integrated circuits (PICs) is a promising approach for low-cost large-scale fabrication considering the CMOS-technology maturity and scalability. However, Si itself cannot provide an efficient emitting light source due to its indirect bandgap. Therefore, the integration of III-V semiconductors on Si wafers allows us to benefit from the III-V emitting properties combined with benefits offered by the Si photonics platform. Direct epitaxy of InP-based materials on 300 mm Si wafers is the most promising approach to reduce the costs. However, the differences between InP and Si in terms of lattice mismatch, thermal coefficients and polarity inducing defects are challenging issues to overcome. III-V/Si hetero-integration platform by wafer-bonding is the most mature integration scheme. However, no additional epitaxial regrowth steps are implemented after the bonding step. Considering the much larger epitaxial toolkit available in the conventional monolithic InP platform, where several epitaxial steps are often implemented, this represents a significant limitation. In this paper, we review an advanced integration scheme of AlGaInAs-based laser sources on Si wafers by bonding a thin InP seed on which further regrowth steps are implemented. A 3 µm-thick AlGaInAs-based MutiQuantum Wells (MQW) laser structure was grown onto on InP-SiO2/Si (InPoSi) wafer and compared to the same structure grown on InP wafer as a reference. The 400 ppm thermal strain on the structure grown on InPoSi, induced by the difference of coefficient of thermal expansion between InP and Si, was assessed at growth temperature. We also showed that this structure demonstrates laser performance similar to the ones obtained for the same structure grown on InP. Therefore, no material degradation was observed in spite of the thermal strain. Then, we developed the Selective Area Growth (SAG) technique to grow multi-wavelength laser sources from a single growth step on InPoSi. A 155 nm-wide spectral range from 1515 nm to 1670 nm was achieved. Furthermore, an AlGaInAs MQW-based laser source was successfully grown on InP-SOI wafers and efficiently coupled to Si-photonic DBR cavities. Altogether, the regrowth on InP-SOI wafers holds great promises to combine the best from the III-V monolithic platform combined with the possibilities offered by the Si photonics circuitry via efficient light-coupling.

Heterogeneous integration of III-V materials onto silicon photonics has experienced enormous progress in the last few years, setting the groundwork for the implementation of complex on-chip optical systems that go beyond single device performance. Recent advances on the field are expected to impact the next generation of optical communications to attain low power, high efficiency and portable solutions. To accomplish this aim, intense research on hybrid lasers, modulators and photodetectors is being done to implement optical modules and photonic integrated networks with specifications that match the market demands. Similarly, important advances on packaging and thermal management of hybrid photonic integrated circuits (PICs) are currently in progress. In this paper, we report our latest results on hybrid III-V on Si transmitters, receivers and packaged optical modules for high-speed optical communications. In addition, a review of recent advances in this field will be provided for benchmarking purposes.

Heterogeneously integrated III-V/Si lasers and semiconductor optical amplifiers (SOAs) are key devices for integrated photonics applications requiring miniaturized on-chip light sources, such as in optical communications, sensing, or spectroscopy. In this work, we present a widely tunable laser co-integrated with a semiconductor optical amplifier in a heterogeneous platform that combines AlGaInAs multiple quantum wells (MQWs) and InP-based materials with silicon-on-insulator (SOI) wafers containing photonic integrated circuits. The co-integrated device is compact, has a total device footprint of 0.5 mm2, a lasing current threshold of 10 mA, a selectable wavelength tuning range of 50 nm centered at λ = 1549 nm, a fiber-coupled output power of 10 mW, and a laser linewidth of ν = 259 KHz. The SOA provides an on-chip gain of 18 dB/mm. The total power consumption of the co-integrated devices remains below 0.5 W even for the most power demanding lasing wavelengths. Apart from the above-mentioned applications, the co-integration of compact widely tunable III-V/Si lasers with on-chip SOAs provides a step forward towards the development of highly efficient, portable, and low power systems for wavelength division multiplexed passive optical networks (WDM-PONs).

In this work, we present an advanced heterogeneous integration scheme which consists in integrating a thin InP layer by wafer-bonding onto a silicon wafer (InPoSi) on which a regrowth step of III-V materials is implemented. Vertical p-i-n AlGaInAs lasers obtained from a single Selective Area Growth (SAG) step on InPoSi were fabricated. Thanks to SAG, the AlGaInAs-MQW structures successfully cover a PL range of 160 nm in the C+L band. Based on these structures, a 5- channel laser array was fabricated. The latter successfully covers a 155 nm-wide spectral band from 1515 nm to 1670 nm with a maximum output power of 20 mW under continuous-wave regime at 20°C. High thermal stability up to 70°C is demonstrated with a characteristic temperature of 69°C for the lasers emitting from 1515 nm to 1600 nm.

We demonstrate a heterogeneously integrated III-V-on-SOI distributed feedback laser with a low grating strength (κ −1) and a narrow linewidth of Δν = 118 kHz. The laser operates single mode with a side-mode suppression ratio over 45 dB, provides a single-sided waveguide-coupled output power of 22 mW (13.4 dBm) and has a wall-plug efficiency of 17%. The dynamic characteristics were also evaluated, obtaining an intrinsic 3 dB modulation bandwidth of 14 GHz and a photon lifetime of 8 ps. Large-signal intensity modulation using a 231-1 PRBS pattern length revealed open eye diagrams up to 25 Gb/s and a penalty on the dynamic extinction ratio lower than 1 dB after transmission over a 2 km standard single mode optical fiber.

Vertical p-i-n lasers integrated by wafer-bonding and regrowth on a heterogeneous InP-on-SOI wafer are presented. We demonstrate for the first time lasers based on regrown III-V active regions efficiently coupled to Si-photonic DBR cavities.

Vertical p-i-n AlGaInAs lasers obtained from a single Selective Area Growth (SAG) step on a thin InP layer bonded to silicon wafers are presented. A PL extension from 1490 nm to 1645 nm was demonstrated on InP-SOI wafer. Based on this result, a record of 155 nm wide spectral range was obtained for FP lasers on InP-SiO 2 /Si wafer.

In this work, we present the fabrication process of a $3~\mu \text{m}$ -thick AlGaInAs-based vertical p-i-n laser diode structure grown on a directly bonded InP-SiO2/Si (InPoSi) substrate. High-quality epitaxial growth on InPoSi is reported. Based on these structures, the fabrication process of Fabry-Perot broad lasers is presented. Device performance is compared to the ones obtained from the same growth run on an InP substrate as a reference. High electrical properties of the n and p contacts are demonstrated. Lasing operation in the pulse regime is shown up to 50°C. Threshold current densities as low as 0.4 kA/cm 2 at 20°C are obtained for the laser on InPoSi, comparable to the ones obtained for the reference on InP substrate.

On-chip optical communications have experienced great progress lately, gaining in maturity with fast, reliable and efficient optical interconnects. Silicon photonics has demonstrated huge potential to become the dominant technology to support this development. Still, the silicon photonics lacks of a monolithic light source. To overcome this blocking point, hybrid integration of III-V materials on silicon raises as a viable route in the short term. In this work, we will revisit the hybrid III-V on Si platform and put forward our particular vision at the III-V lab, discussing several points that will play a key role in the coming years.

Fabry-Perot laser arrays based on vertical p-i-n laser diode structures grown on InP layer directly bonded to Si wafer is presented. Lasing emission covering the C+L bands is achieved by means of a single-epitaxy Selective Area Growth (SAG) technology.

International audience

Epitaxial growth of high material quality $1.55\boldsymbol{\mu} \mathbf{m}$ AlGaInAs Multiquantum Wells Heterostructure on a directly-bonded InPoSi substrate has been developed for datacom applications.

Monolithic two‐terminal III‐V on Si dual‐junction solar cells, designed for low concentration applications, were fabricated by means of surface‐activated direct wafer bonding. The III‐V top cell is a heterojunction formed by an n‐Ga₀.₅In₀.₅P emitter and a p‐Al₀.₂Ga₀.₈As base. An efficiency of 21.1 ± 1.5% at one sun and 23.7 ± 1.7% at 10 suns is demonstrated, which to our knowledge is the best dual‐junction two‐terminal III‐V on Si tandem cell efficiency reported to date under verified reference conditions. The I‐V characterization of these 1‐cm² tandem cells under concentration required the development of a new method using a single‐source multiflash solar simulator and not perfectly matched component cells, also known as pseudo‐isotypes, formed by Si single‐junction cells and optical filters. In addition, the spectrum of the pulsed solar simulator was measured using a high‐speed CMOS spectrometer, allowing the calculation of the spectral mismatch correction factor. Merging these two techniques results in the hybrid corrected pseudo‐isotype (HCPI) characterization method, which shows a fast and accurate performance with a simplified procedure based on a single‐source solar simulator. Pseudo‐isotypes are easily adaptable to new cell designs by simply using a different filter, hence allowing the characterization of new multijunction solar cell architectures.

MOVPE regrowth of III-V materials on a directly-bonded InP-SiO2/Si (InPoSi) membrane is of particular interest to transpose the III-V mature multi-regrowth technologies [1][2][3] from the InP substrate classical platform into the hybrid III-V on Si platform [4]. MOVPE requires high-temperature elevation, typically above 600°C. We have shown for the first time void formation in a directly bonded InPoSi membrane at high temperature (400°C) despite the use of a thick oxide at the bonding interface [5]. The demonstration of highly efficient outgassing trenches under high temperature annealing as well as MOVPE regrowth of a high-quality III-V heterostructure was obtained. Subsequent improvements in the treatments of the bonded surfaces allowed to achieve MOVPE regrowth of high-quality III-V material without the use of any outgassing methods [6]. In particular, a compressive strain of 400 ppm at growth temperature was shown for the first time by curvature measurements carried out during growth. The latter is due to the difference of thermal coefficients between InP and Si [7]. Despite this thermal strain, a 3 μm-thick laser structure was successfully grown on InPoSi and compared to the same structure on InP as a reference [8]. Device performance are similar for both structures showing that there is no penalty induced by regrowing μm-thick structures onto InPoSi in spite of the thermal strain. References [1] V. Rustichelli et al., “Monolithic integration of buried-heterostructures in a generic integrated photonic foundry process,” IEEE J. Sel. Top. Quantum Electron., vol. 25, no. 5, Sep. 2019 [2] N. Dupuis et al., “10-Gb/s AlGaInAs Colorless Remote Amplified Modulator by Selective Area Growth for Wavelength Agnostic Networks,” IEEE Photonics Technol. Lett., vol. 20, no. 21, pp. 1808–1810, 2008. [3] H. Debregeas et al., “TWDM-PON Burst Mode Lasers with Reduced Thermal Frequency Shift,” J. Light. Technol., vol. 36, no. 1, pp. 128–134, Jan. 2018. [4] B. Szelag et al., “Hybrid III–V/Silicon Technology for Laser Integration on a 200-mm Fully CMOS-Compatible Silicon Photonics Platform,” IEEE J. Sel. Top. Quantum Electron., vol. 25, no. 5, pp. 1–10, Mar. 2019. [5] C. Besancon et al., “Kinetic study of hydrogen lateral diffusion at high temperature in a directly-bonded InP-SiO2/Si substrate,” Nanotechnology, vol. 31, no. 13, p. 135205, Mar. 2020. [6] C. Besancon et al., “Epitaxial Growth of High-Quality AlGaInAs-Based Active Structures on a Directly Bonded InP-SiO2/Si Substrate,” Phys. Status Solidi Appl. Mater. Sci., vol. 217, no. 3, Feb. 2020. [7] K. Takeda, S. Matsuo, T. Fujii, K. Hasebe, T. Sato, and T. Kakitsuka, “Epitaxial growth of InP to bury directly bonded thin active layer on SiO2/Si substrate for fabricating distributed feedback lasers on silicon,” IET Optoelectron., vol. 9, no. 4, pp. 151–157, 2015. [8] C. Besancon et al., “Comparison of AlGaInAs-Based Laser Behavior Grown on Hybrid InP-SiO₂/Si and InP Substrates,” IEEE Photonics Technol. Lett., vol. 32, no. 8, pp. 469–472, Apr. 2020.