chanelink logo
CHANELINK
Español

Medium-long wavelength infrared quantum cascade laser of MOCVD on silicon

442
2023-08-04 16:26:34
Ver traducción
Us researchers report 8.1 μm wavelength quantum cascade laser (QCL) grown on silicon (Si) by MOCVD [S. Xu et al., Applications. Physics Letters, v123, p031110, 2023]. "There are no previous reports of QCL growth on silicon substrates by metal-organic chemical vapor deposition (MOCVD)," commented the team from the University of Wisconsin-Madison, the University of Illinois at Urbana-Champaign and MicroLink Devices Inc.
 
This integration on silicon could lead to the development of chip scale, reliable and mass-producible photonic integrated circuits (PIC). The researchers contrast this with other integration methods such as wafer bonding: "Hybrid integration methods rely on precise alignment to achieve efficient waveguide to laser optical coupling, which in turn requires tight fabrication machining tolerances. Direct integration onto silicon through heteroepitaxy enables mid-infrared (IR) optoelectronic devices to be integrated with mature CMOS-compatible silicon platforms at low cost and high throughput."
 
Mid-infrared QCL is usually grown on indium phosphide (InP). The team paid particular attention to creating a virtual InP substrate on silicon by combining molecular beam epitaxy (MBE) and MOCVD. MOCVD is superior to MBE in production. "The remaining technical challenge is to overcome the defects and epitaxial growing-related problems caused by large lattice constant and thermal expansion mismatches (e.g., about 8% lattice mismatches) and about 50% thermal expansion coefficient mismatches between InP and primary substrates such as silicon," the researchers comment.
The arsenide portion of the template structure (Figure 1) is a limited company grown on a commercial (001) GaP/Si template (supplied by NAsP III/V) using a solid source MBE. The substrate is nominally coaxial and compatible with high-throughput industrial-scale CMOS electronics production. The initial layer consists of an Indium Gallium Arsenide (InGaAs) dislocation filter layer (DFL) sandwiched in GaAs. By keeping the thickness of the initial arsenide layer at 0.5 μm, the researchers sacrificed some of the potential for reducing the penetration dislocation density (TDD). The GaAs layer grows in two steps, first at low temperatures of 500°C and then at higher temperatures (580/610°C for the lower/upper layers, respectively). As far as the upper layers are concerned, one motivation for doing so is to avoid the escape of indium in InGaAs DFL.
 
The upper InP metaseptic buffer (MBL) portion of the template grows through MOCVD and includes four additional DFLS, consisting of three 2nm/37nm InAs/InP pairs.
 
The QCL is completed using MOCVD and has a total epitaxial thickness (including the metamorphic buffer layer and the laser layer) of approximately 13 μm. QCL/Si did not show cracks, which the team believes could be due to two factors: the small sample size of 1.7cmx1.7cm, and the curvature accumulation mitigated by the 800 μm thick silicon substrate. The TDD for the arsenide portion of the template was estimated to be 1.0 x109 / cm-2. InP MBL reduces this to 7.9x108 /cm 2.
Under pulsed operation, the threshold current density on silicon is 22% lower than that of devices grown on bulk InP substrates during the same process run: in the figure, 1.50kA/cm 2 and 1.92kA /cm 2, respectively. The researchers comment: "This may reflect reduced incorporation of silicon dopants within the active nuclear superlattices due to pre-existing defects or differences in the growth temperatures of the silicon and InP substrate surfaces. In addition, uneven growth around the defect site may reduce carrier mobility and tunneling efficiency, which would explain the higher series resistance observed in devices grown on silicon."
 
The higher the voltage required to provide a given current injection in a silicon-based QCL, the higher the series resistance. Despite the higher series resistance, silicon-based QCL also provides higher peak optical output power: 1.64W for silicon-based devices and 1.47W for INP-based devices. The corresponding slope efficiency is 0.72W/A and 0.65W/A, and the electro-optical conversion efficiency is 2.85% and 2.50%, respectively.
 
The emission spectral analysis showed a variety of modes in the wavelength range 7.6-8.3 μm. The maximum peak values of InP and Si based devices are about 8.1 μm and 8.0 μm, respectively. These wavelengths are slightly shorter than the design target of 8.2 μm. The researchers believe that this difference may be due to local growth changes affecting layer thickness, as shown in X-ray diffraction analysis.
 
Source: Laser Network
Recomendaciones relacionadas

  • Nankai University makes progress in the field of free electron photon interactions

    Recently, a research team led by Professor Cai Wei and Professor Xu Jingjun from the School of Physical Sciences at Nankai University has experimentally confirmed for the first time the generation of polaritons, also known as Smith Purcell radiation, at the two-dimensional scale, and further demonstrated the ability of free electrons to regulate two-dimensional Smith Purcell radiation. The researc...

    02-11
    Ver traducción

  • Coherent lasers will help expand the scale of fusion tokamaks

    Coherent company's excimer lasers can be more widely used in fusion reactor applications, after the US based photonics giant signed a "letter of intent" with Japan's Faraday 1867 Holdings.Faraday 1867, headquartered in Kanagawa Prefecture, is said to have become the world's leading manufacturer of high-temperature superconducting (HTS) tape through its subsidiary Faraday Japan factory.This tape is...

    2023-10-11
    Ver traducción

  • MIT research enables 3D printers to recognize new materials

    According to scientists at MIT, mathematical formulas developed by MIT researchers and other institutions can significantly improve the sustainability of 3D printing.Issues with 3D printing of plastics3D printers typically use mass-produced polymer powders to print parts, which are consistent and predictable, but also difficult to recycle.Other more environmentally friendly options also exist and ...

    2024-04-18
    Ver traducción

  • Emerging laser technologies for precise manufacturing of multifunctional nanomaterials and nanostructures

    The use of photons to directly or indirectly drive chemical reactions has fundamentally changed the field of nanomaterial synthesis, leading to the emergence of new sustainable laser chemistry methods for manufacturing micro - and nanostructures. The incident laser radiation triggers complex interactions between chemical and physical processes at the interface between solid surfaces and liquid or ...

    2024-08-05
    Ver traducción

  • Multiple international laser companies continue to increase investment in the Chinese market

    In early spring of 2025, China's laser industry once again attracted the attention of global laser giants, ushering in a new wave of international investment boom.After several global laser giants accelerated their layout in China in 2024, in February 2025, Carl Zeiss from Germany and Bystronic from Switzerland, two global giants in the optical and laser fields, also announced significant expansio...

    02-15
    Ver traducción