[Paper Review] GaAs nano-ridge laser diodes fully fabricated in a 300 mm CMOS pilot line

Yannick De Koninck, Charles Caër+15 more|arXiv (Cornell University)|Jul 20, 2023

Photonic and Optical DevicesEngineering3 citations

TL;DR

This paper demonstrates the first electrically driven GaAs-based multi-quantum-well laser diodes fully fabricated on 300 mm silicon wafers in a CMOS pilot line. Using selective-area epitaxy with aspect-ratio trapping, the authors achieve room-temperature continuous-wave lasing at ~1020 nm with threshold currents as low as 5 mA, output powers exceeding 1 mW, and linewidths down to 46 MHz across more than 300 devices per wafer, proving the feasibility of monolithic III-V/Si laser integration for scalable photonic applications.

ABSTRACT

Silicon photonics is a rapidly developing technology that promises to revolutionize the way we communicate, compute, and sense the world. However, the lack of highly scalable, native CMOS-integrated light sources is one of the main factors hampering its widespread adoption. Despite significant progress in hybrid and heterogeneous integration of III-V light sources on silicon, monolithic integration by direct epitaxial growth of III-V materials remains the pinnacle in realizing cost-effective on-chip light sources. Here, we report the first electrically driven GaAs-based multi-quantum-well laser diodes fully fabricated on 300 mm Si wafers in a CMOS pilot manufacturing line. GaAs nano-ridge waveguides with embedded p-i-n diodes, InGaAs quantum wells and InGaP passivation layers are grown with high quality at wafer scale, leveraging selective-area epitaxy with aspect-ratio trapping. After III-V facet patterning and standard CMOS contact metallization, room-temperature continuous-wave lasing is demonstrated at wavelengths around 1020 nm in more than three hundred devices across a wafer, with threshold currents as low as 5 mA, output powers beyond 1 mW, laser linewidths down to 46 MHz, and laser operation up to 55 °C. These results illustrate the potential of the III-V/Si nano-ridge engineering concept for the monolithic integration of laser diodes in a Si photonics platform, enabling future cost-sensitive high-volume applications in optical sensing, interconnects and beyond.

Motivation & Objective

• To enable monolithic integration of III-V laser diodes on silicon for scalable, cost-effective photonic integrated circuits.
• To overcome the challenge of integrating high-quality, electrically pumped III-V light sources directly on silicon substrates in a standard CMOS manufacturing environment.
• To demonstrate wafer-scale fabrication of GaAs-based nano-ridge waveguides with embedded p-i-n diodes and InGaAs quantum wells using selective-area epitaxy.
• To validate the performance of these lasers under continuous-wave operation at room temperature across an entire 300 mm wafer.

Proposed method

• Utilized selective-area epitaxy with aspect-ratio trapping to grow high-quality GaAs nano-ridge waveguides on 300 mm Si wafers.
• Integrated InGaAs multi-quantum-well active regions and InGaP passivation layers within the nano-ridge structure for efficient carrier confinement and optical guiding.
• Performed III-V facet patterning and standard CMOS-compatible contact metallization processes in a pilot-line environment to ensure process compatibility.
• Employed p-i-n diode structures embedded in the nano-ridges to enable electrical injection and optical gain.
• Conducted full electrical and optical characterization across more than 300 devices per wafer to assess performance uniformity and scalability.

Experimental results

Research questions

• RQ1 Can GaAs-based multi-quantum-well laser diodes be monolithically integrated on 300 mm silicon wafers using a standard CMOS pilot-line process flow?
• RQ2 What is the performance of electrically driven GaAs nano-ridge lasers in terms of threshold current, output power, and linewidth when fabricated at scale?
• RQ3 To what extent can selective-area epitaxy with aspect-ratio trapping enable high-quality III-V material growth on silicon substrates for photonic devices?
• RQ4 Can the fabricated lasers achieve continuous-wave operation at room temperature across an entire 300 mm wafer with consistent performance?
• RQ5 How does the integration of InGaP passivation layers and p-i-n diodes impact device efficiency and reliability in this platform?

Key findings

• Room-temperature continuous-wave lasing was achieved at a wavelength of approximately 1020 nm across more than 300 devices on a single 300 mm wafer.
• The lasers exhibited threshold currents as low as 5 mA, indicating high electrical efficiency and low optical loss.
• Output powers exceeded 1 mW, demonstrating sufficient optical output for practical on-chip interconnect and sensing applications.
• Laser linewidths were measured down to 46 MHz, indicating high spectral purity and suitability for coherent communication.
• Laser operation was stable up to 55 °C, confirming thermal robustness under practical operating conditions.
• The entire fabrication process, including III-V epitaxy, patterning, and metallization, was successfully executed in a 300 mm CMOS pilot line, proving process scalability and compatibility.