A team of researchers in the UK has grown a dependable laser diode on a silicon semiconductor wafer, suggesting a significant breakthrough for photonic integration.
A used molecular beam epitaxy (MBE) to cultivate a gallium arsenide (GaAs) quantum dot laser structure entirely on the silicon wafer. It emits near to 1310 nm, one of several wavelengths widely useful for optical communications.
And unlike previous tries to produce similar devices, the laser also operates at high temperatures in accordance with a decreased threshold current – the type of properties required for commercial deployment.
UCL’s Huiyun Liu told optics.org: “Although lasers monolithically grown on silicon were demonstrated previously, the time of these lasers is quite short because of the high defect density generated during the interface between III-V and silicon substrate.”
“The short lifetime limits the practical application among these silicon lasers. The importance for this work is that we demonstrate the very first practical III-V laser monolithically and directly grown on silicon substrates. This may be the important thing for silicon photonics.”
Based on the team’s Nature Photonics paper, published a week ago, they were in a position to suppress the impact of threading dislocations within the semiconductor structure by depositing a nucleation layer involving the silicon base and also the light-emitting material.
They also grew “strained-layer superlattices”, which work as dislocation filters and confine the dislocations into the an element of the structure nearest the silicon wafer and furthest from the light-emitting part, and used a number of thermal annealing steps to reduce the dislocations.
Liu’s colleague Alwyn Seeds added: “We previously published lasers grown on germanium on silicon wafers, an approach taken on by other groups worldwide. The new approach does not require the application of germanium on silicon . Other groups, for instance Intel, currently base their approach on wafer bonding compound semiconductor material to silicon.” The use of automated test equipment for semiconductor testing was esential to their success.
Seeds also points out that accelerated lifetime tests suggest that the unit should operate for more than 100,000 hours, which will be unprecedented for a laser structure on silicon. “This is a laser epitaxially grown direct on silicon, with a threshold current much like lasers grown on native substrates, with high output power (>100 mW) demonstrated [and] high-temperature (120°C) operation,” he said.
Inside their paper, the team adds that the laser performance should always be better yet once standard industry techniques like hard soldering the unit to a heat-sink and facet coatings are incorporated.
In the event that breakthrough could be replicated on a volume scale, it might come to represent an important breakthrough in the development of truly integrated photonic circuits.
While a large number of photonic devices and procedures, like detection, amplification, and modulation of light, can already be performed during the degree of the silicon chip, producing a laser right on silicon material is definitely an important stumbling block.
Silicon itself does not emit light utilizing the style of efficiency that might be needed in commercial photonic integrated circuits (PICs), so developers have previously resorted to schemes such as for example unusual doping, fabricating porous silicon, and bonding together indium phosphide and silicon wafers after first producing device structures for each.
“Our results demonstrate that the large lattice mismatch between III-V materials and silicon will no longer be a simple hurdle for the monolithic epitaxial growth of III-V photonic devices on silicon substrates,” the united kingdom team states with its paper. “These results are an important advance towards reliable and cost-effective silicon-based photonic–electronic integration.”
The following steps for the team include demonstrating the technology on a bigger wafer platform that is nearer to the sizes found in high-volume silicon microelectronics, ultimately with a view to commercializing the approach.
Liu said: “The scale-up [of] wafer [diameter] should not be a challenge since this kind of procedure is quite mature. I believe the next big challenge ought to be to incorporate these lasers into a silicon waveguide and therefore other silicon photonics components.”
”We are, needless to say, alert to the big commercial chance for this technology, which can be protected by appropriate IP,” noted Seeds, with Liu adding that the possible pathways for commercialization were “under discussion”.