Silicon is the most common material in the semiconductor industry. Silicon based electronic chips are widely used in everyday devices, from smartphones, computers, to cars, airplanes, and satellites. As technology evolves, researchers have found that chip-to-system communication over traditional electrical interconnects has made it difficult to meet faster communication speeds and more complex system requirements between electronic devices. To solve this problem, "Light" is considered as a very promising ultra-high-speed transmission medium, which can be used for data communication between silicon-based chips and systems. However, silicon, as an indirect bandgap material, has extremely low luminous efficiency and is difficult to directly use as a light-emitting material. Researchers have proposed using the Group III-V materials with high luminous efficiency as luminescent materials to grow or bond to silicon substrates for silicon-based optoelectronic integration. Group III nitride materials are a kind of direct band gap materials with broad bandgap width, strong chemical stability, high breakdown electric field and high thermal conductivity. They are widely used in high efficiency light emitting devices and power electronic devices , In recent years has become a major research hotspot. The InGaN-based laser grown directly on the silicon substrate material for the GaN-based optoelectronic devices and silicon-based optoelectronic devices possible integration. On the other hand, InGaN-based lasers have been rapidly developed in more than 20 years since their introduction in 1996. Their applications range from information storage, lighting, laser display, visible light communication, subsea communication, and biomedical applications. At present, almost all InGaN-based lasers are fabricated with expensive self-supporting GaN substrates, which limits their application. The silicon substrate has the advantages of low cost, high thermal conductivity and large wafer size. If the InGaN-based laser can be fabricated on a silicon substrate, its production cost will be effectively reduced, thereby further promoting its application.
Due to the huge lattice constant mismatch and thermal expansion coefficient mismatch between the GaN material and the silicon substrate, growing the GaN material directly on the silicon substrate results in high GaN film dislocation density and easy to crack, so the silicon substrate InGaN-based lasers are difficult to make. This research direction is the hot spot in the world at present, but so far, only the article reports the excitation of the InGaN-based MQW structure on the silicon substrate under optical pumping.
In response to this key scientific and technological issue, the Group III nitride semiconductor materials and devices research team led by Yang Hui, a research fellow at the Suzhou Institute of Nanoscience and the Academia Sinica, adopted an AlN / AlGaN buffer layer structure to effectively reduce the dislocation density while successfully suppressing the defects of silicon and GaN Materials such as the thermal expansion coefficient mismatch and often caused by the crack, the growth of the thickness of the InGaN-based laser structure on the silicon substrate to a thickness of about 6 μm, the dislocation density of less than 6 × 108 cm-2, and through the device technology, successfully achieved The world's first silicon substrate InGaN-based laser excited at room temperature under continuous electron injection has a lasing wavelength of 413 nm and a threshold current density of 4.7 kA / cm2.
The project has been supported by the CASS Frontier Science and Education Bureau, the Pilot Project of Chinese Academy of Sciences, the National Natural Science Foundation of China, the Ministry of Science and Technology's key R & D Program, and the Suzhou Institute of Nanoscience and Technology, Chinese Academy of Sciences, as well as the processing platform and testing platform of Suzhou Institute of Nanotechnology Nano-X technical support. Relevant research results were published online in the August 15 online journal Nature Photonics (2016 latest Impact Factor 31.167).
Silicon substrate InGaN-based semiconductor laser
Structure diagram of Si substrate InGaN-based laser
Test results of InGaN based laser on Si substrate
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