Quantum Dot Lasers on Silicon Substrates

Quantum dot lasers epitaxially integrated on silicon substrates represent a convergence of III–V semiconductor light sources with mature silicon photonic platforms. By embedding nanoscale quantum dots within laser structures grown directly on silicon, researchers exploit the superior defect tolerance and discrete energy levels of quantum dots to mitigate the deleterious effects of lattice and thermal mismatch. This approach promises on-chip coherent light sources fully compatible with complementary metal-oxide-semiconductor fabrication, enabling dense photonic integration for data-centre interconnects, optical communications at telecommunications wavelengths and emerging photonic computing architectures. Key challenges include managing antiphase boundaries, threading dislocations and strain during heteroepitaxial growth, while achieving low threshold currents, high output power and reliable continuous-wave operation at elevated temperatures. Recent advances in epitaxial templates, dislocation filters and waveguide coupling have demonstrated monolithic lasers with sub-milliamp thresholds, multi-milliwatt output and projected lifetimes extending to decades. The global significance of this technology lies in its potential to deliver compact, low-cost, energy-efficient light sources directly on silicon wafers, thereby transforming both classical optical networks and on-chip photonic circuits.

Research from Nature Portfolio

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Research from all publishers

In 2023, a monolithic integration strategy employed patterned silicon-on-insulator trenches and hybrid molecular beam epitaxy to embed InAs/GaAs quantum dot lasers directly on SOI. Butt-coupled silicon waveguides achieved continuous-wave lasing up to 85 °C with output powers near 7 mW and coupling efficiencies around –6.7 dB, demonstrating scalable on-chip light sources without intermediate bonding.

Also in 2023, analysis of templated epitaxy in narrow oxide pockets revealed that aligning all pockets to a specific crystal direction of the III–V material dramatically reduces material asymmetry and threading dislocations. This alignment rule enhances device yield and performance for electrically pumped quantum dot lasers on patterned silicon photonic wafers, paving the way for high-volume manufacturing on 300 mm substrates.

In 2021, improvements in dislocation filtering—through combined misfit and threading dislocation barriers—lowered defect densities to the 10⁶ cm^–2 range for InAs quantum dot lasers on on-axis silicon. Devices exhibited record reliability under 80 °C stress, with negligible degradation over 1 200 h and an extrapolated median lifetime exceeding 20 years, marking a critical step towards practical deployment in telecommunications and data-centre environments.

Quantum Dot Lasers on Silicon Substrates publication trend

The graph below shows the total number of articles in quantum dot lasers on silicon substrates across all publications each year (not limited to Nature Index journals).

Technical terms

Quantum dot: A nanoscale semiconductor particle that confines carriers in all three dimensions, producing discrete energy states and reduced sensitivity to crystalline defects.

Epitaxy: The process of growing a crystalline layer on a substrate, where the deposited film adopts the crystallographic orientation of the underlying material.

Threading dislocation: A crystallographic defect that propagates through an epitaxial layer from the interface, often degrading optical and electrical performance.

Threshold current density: The minimum current per unit area required to achieve population inversion and initiate lasing in a semiconductor laser.

Continuous-wave lasing: Steady-state laser emission under constant electrical or optical pumping, as opposed to pulsed operation.

References

1. Design Rules for Addressing Material Asymmetry Induced by Templated Epitaxy for Integrated Heteroepitaxial On‐Chip Light Sources. Advanced Functional Materials (2023).
2. Monolithic integration of embedded III-V lasers on SOI. Light: Science & Applications (2023).
3. 1.3  μm submilliamp threshold quantum dot micro-lasers on Si. Optica (2017).
4. High-temperature reliable quantum-dot lasers on Si with misfit and threading dislocation filters. Optica (2021).