Applications of Semipolar Gallium Nitride (GaN)

Seren Photonics Semipolar Gallium Nitride (GaN) templates

Although Semipolar Gallium Nitride (GaN) offers significant benefits across a wide range of devices such as sensors, GaN HEMT transistors and green lasers, Seren Photonics’ primary market focus is on LEDs, where Seren Photonics’ Semipolar GaN products target the industry’s two main problems:-

  • The Green Gap; the very low efficiency of green LEDs
  • Efficiency Droop; the significant problem where LEDs become less efficient at higher powers

Emerging 	applications for Seren’s semipolar enabled LEDs include Li-Fi visible light communication (VLC) The lack of an efficient green LED affects all applications where an RGB solution is required, such as in displays or smart colour ambience lighting, limiting the rate of adoption of such technologies due to poor performance or high cost. By enabling an efficient green LED, fewer LEDs are required, leading to significant cost savings. In addition to the major opportunities we show below, another emerging application for Seren Photonics’ Semipolar enabled LEDs includes Li-Fi visible light communication (VLC) that can offer significant data rates compared to some Wi-Fi networks and could become part of a network 5G solution.

MicroLEDs for Next Generation Displays

Reducing Cost

Current green LEDs are so inefficient in display use that two green pixels are needed for every one red and blue One of the fastest growing markets for LEDs is in next generation displays, where microLEDs are used as the direct-emitting pixel – this requires a red, a blue and a green sub-pixel (the microLED). MicroLEDs are an attractive display solution with superior performance, even compared to OLED displays, and feature:

  • Lower power consumption
  • Higher brightness
  • Wider colour gamut
  • Fast refresh rates

These features have attracted significant interest from major multi-nationals, with Apple, Facebook, Foxconn and Google all having made acquisitions or major investments in microLED display technology in the last 3 years. However, because today’s green LEDs are so inefficient, two green pixels are needed for every one red and blue even taking into account that the eye is more sensitive to the green.

This means that the screen resolution cannot be maximised; ie pixels per inch (PPI), where a pixel is defined as the total area of the red, the green and the blue sub-pixels. Furthermore, a low efficiency green sub-pixel consumes significantly more power than it should, which ultimately reduces one of the main benefits of using microLED display technology; power consumption. Through using semipolar GaN, the efficiency of green LEDs can be improved eliminating the need for two green microLEDs per pixel.

Colour Stability

Seren’s semipolar GaN has been demonstrated to provide significant wavelength stability for green LEDs compared to commercially available LEDs A unique benefit of Seren Photonics’ Semipolar GaN is it's colour stability, that cannot be achieved using conventional polar GaN. In a display, the colour emitted from each pixel is a combination of the light from the individual RGB sub-pixels and is controlled through power and modulation to each. Today’s green LEDs made on conventional c-plane GaN not only suffer from poor efficiency, but also poor colour stability at different operating conditions, where the colour emitted from the pixel varies depending on the power provided. This is a serious problem in displays significantly affecting the quality and colour accuracy of the final image as the final colour emitted is very sensitive to the power and wavelength of the three primary RGB colours.

Seren Photonics’ Semipolar GaN provides significant wavelength stability for green LEDs compared to commercially available LEDs as can be seen from the image above. This unique property is only achieved through the elimination of the electric fields within the GaN semiconductor, which is a fundamental property of semipolar GaN and cannot be achieved in polar-GaN.

High power point source LEDs

Seren Photonics Semipolar Gallium Nitride (GaN) templates for next generation microLED displays

Much of the fundamental problems that result in the green gap are also in evidence in efficiency droop, albeit, they occur at much higher operating powers in blue LEDs (normally used for high power white light LED source). Many applications require a very bright white light source with a very small footprint. This might include automotive headlamps and smart phone flash. In both cases, the design aspects dictate that the light source is very small in order not to affect the overall design.

To achieve high brightness requires high power. Problems arise when the LED efficiency drops below a critical level where more power is now converted into heat and not light, which leads to overheating and typically catastrophic failure. The fundamental properties of semipolar GaN offer a means of targeting efficiency droop leading to higher efficiency at higher powers; ie more light from a smaller LED.

The Seren Photonics segment addressable market (SAM) derived from these applications exceeds $0.5B and is expected to grow rapidly as microLED enabled next generation displays begin to emerge in consumer products such as wearables and smart phones.

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