Hybrid Silicon Lasers for Photonic Devices

The heterocore microcavity is realized via ultrathin silicon dioxide interlayer bonding of III–V on SOI and dual hard mask technique. (Source: A-Star / ACS)

Producing semi­conductor lasers on a silicon wafer is a long-held goal for the elec­tronics industry, but their fabri­cation has proved challenging. Now, researchers at A-STAR have developed an inno­vative way to manu­facture them that is cheap, simple and scalable. Hybrid silicon lasers combine the light-emitting pro­perties of group III–V semi­conductors, like gallium arsenide and indium phos­phide, with the maturity of silicon manu­facturing techniques.

These lasers are attracting consi­derable attention as they promise inex­pensive, mass-pro­ducible optical devices that can inte­grate with photonic and micro­electronic elements on a single silicon chip. They have potential in a wide range of appli­cations, from short-distance data communi­cation to high-speed, long-distance optical trans­mission. In the current pro­duction process, however, lasers are fabri­cated on separate III–V semi­conductor wafers before being indi­vidually aligned to each silicon device. A time-consuming, costly process that limits the number of lasers that can be placed on a chip.

To overcome these limi­tations, Doris Keh-Ting Ng and her colleagues from the A-STAR Data Storage Insti­tute have developed an inno­vative method for producing a hybrid III–V semi­conductor and silicon-on-insu­lator optical microcavity. This greatly reduces the com­plexity of the fabri­cation process and results in a more compact device. “It’s very chal­lenging to etch the entire cavity,” says Ng. “Currently, there is no single etch recipe and mask that allows the whole micro­cavity to be etched, and so we decided to develop a new approach.”

By first attaching a thin film of III–V semi­conductor to a silicon oxide wafer using a SOI inter­layer thermal bonding process, they produced a strong bond that also removes the need for strong oxidizing agents, such as Piranha solution or hydro­fluoric acid. And by using a dual hard-mask technique to etch the micro­cavity that confined etching to the intended layer, they eli­minated the require­ment to use multiple overlay litho­graphy and etching cycles.

“Our approach cuts down the number of fabri­cation steps, reduces the use of hazardous chemicals, and requires only one litho­graphy step to complete the process,” explains Ng. The work presents, for the first time, a new hetero­core confi­guration and integrated fabri­cation process that combines low-tem­perature SiO2 inter­layer bonding with dual hard-mask, single litho­graphy patterning. “The process not only makes it possible to produce hetero­core devices, it also greatly reduces the challenges of fabri­cating them, and could serve as an alter­native hybrid micro­cavity for use by the research community,” says Ng. (Source: A-Star)

Reference: C.-W- Lee et al.: Fabrication and Demonstration of III-V/Si Heterocore Microcavity Lasers via Ultrathin Interlayer Bonding and Dual Hard Mask Techniques, ACS Phot. 3, 2191 (2016); DOI: 10.1021/acsphotonics.6b00794


Link: Data Storage Institute DSI, Agency for Science, Technology and Research A-STAR, Singapore

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