KYOCERA develops new, world’s smallest* mass-produced GaN laser chip made of silicon working substrate

The company is unveiling a new process to create micro-light sources operating at 100 microns in length with higher throughput and lower cost – enabling the use of short-lumen lasers and small LEDs for self-driving, augmented reality and virtual reality applications.

Kyocera Corporation (President: Hideo Tanimoto) has developed a new thin-film processing technology to make unique silicon (Si) substrates for gallium nitride (GaN)-based micro-light sources, including short-lumen lasers and micro-LEDs.

* World’s Smallest: Among the GaN-based edge-emitting lasers on silicon substrates. (Source: Kyocera, September 2022)

what or what Is it an accurate light source?

A “micro light source” is a light source with a side measuring less than 100 microns (1/10 of a millimeter). Examples include short-lumen lasers and small LEDs. Because they provide key performance advantages, such as higher clarity, smaller size, and lighter weight, precision light sources are essential for next-generation automotive displays, smart wearable glasses, communication equipment, and medical devices. The miniature LED chips market alone is expected to reach $2.7 billion by 2026, a compound annual growth rate (CAGR) of around 241%. *

*Source: TrendForce “Small Size LED Display Chip Market To Be Expected To Reach $2.7 Billion By 2026, Says TrendForce” (August, 2022)

Technical challenges in making accurate light sources

GaN-based light source devices, both miniature LED and laser, are typically manufactured on sapphire and GaN substrates. Conventional processes involve forming a thin film of a light source GaN device directly on a sapphire substrate by heating it to a high temperature (1,000 °C or more) in a controlled gas atmosphere. The device layer must then be removed, or ‘peeled off’ from the substrate to create a GaN-based micro-light source device. Despite the growing demand for smaller devices, there are three separate challenges that threaten the ability of this process to achieve its miniaturization goals in the near future:

Difficulty peeling off the device layer

In the case of small LEDs, current processes require difficult steps to split the device layer into individual light sources on the substrate; And then, to separate (or “peel”) the device layer off the substrate. As devices get smaller, the technical challenge of this peeling process can lead to unacceptably low throughput.

High density of defects, inconsistent quality

Fabrication of precise light sources is also a problem because device layers must be deposited on sapphire, silicon, or other materials with crystal structures different from those of the device layer. This creates a high density of defects and inherent quality control challenges.

high manufacturing costs

GaN and sapphire substrates are expensive materials. Although silicon substrates cost less than sapphire, separating the device layer from the silicon substrate is very difficult.

A new process developed by Kyocera

Kyocera has successfully developed the new processing technology at the company’s Research Institute for Advanced Materials and Devices in Kyoto, Japan. First, we grow a GaN layer on a Si substrate which is available in large quantities and at low cost. The GaN layer is then masked with a non-growth material that has a hole in the center. Then, when a GaN layer is formed on the Si substrate, GaN cores grow above the hole in the mask. The GaN layer, which is a growing nucleus, has many defects in the initial stage of growth; But, by forming the GaN layer laterally, high-quality GaN layers with low defect density can be generated, and devices can be successfully fabricated from this low defect region of the GaN layer.

Advantages of the new Kyocera process

Easier peeling of the GaN device layer

Masking the GaN layer with a non-growth material inhibits the bonding between the Si substrate and the GaN layer, which greatly simplifies the exfoliation process.

High quality GaN device layers with low defect density

Since the Kyocera process can deposit low-defect GaN over a wider area than before, it is possible to uniformly fabricate high-quality device layers.

Lower manufacturing costs

The new Kyocera method facilitates the successful and reliable separation of the GaN device layer from the relatively inexpensive Si substrate, which significantly reduces manufacturing costs.

Micro light source applications

Next-generation car transparent screen

In the future, the advent of self-driving will create a demand for brighter, higher definition, energy-saving, more transparent, and less expensive displays.

Next-generation car transparent screen

Partial Light Sources for AR/VR

The market for precision light sources used in augmented reality (AR) and virtual reality (VR) is expected to expand rapidly. Smart glasses and other products are being developed to facilitate the creation of virtual spaces through the metaverse in VR and “de-smartphoning” in AR. While the traditional AR semiconductor laser has been scaled down to 300 microns in length, Kyocera is the first in the world to reach just 100 microns in size. We can achieve this scale by developing an entirely new production process that is an evolution of the slitting method.

The so-called “new slit method” results in a volume reduction of about 67% and helps reduce energy consumption. Semiconductor lasers with low power consumption make it possible to reduce the size and weight of the battery, thus improving the fit.

augmented reality glasses

Kyocera will offer a wide range of platforms, substrate, and processing technologies to bring high-quality, low-cost precision light sources to market in the near future. We also aim to transform the next generation display and laser markets with this new platform.

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