High-power LED market usage is expanding. The use of these devices in industrial lighting applications leads to high efficiency. It is because the higher the efficiency, the lower the heat, and ultimately, the more simple heat management, cheap.
In view of the state of the LED industry, many chip manufacturers are working to improve the efficiency of the equipment, and in the large power industry to get more success and greater profit margins. Even if these equipment manufacturers are only a few percent more efficient than their peers, this will give them a considerable advantage, and they can have a lot of profit margins, a large part of which comes from the production of high-end LED chips.
Another advantage of being able to produce high-efficiency equipment is that if they are also reliable, they can succeed in the automotive headlamps. However, they are not successful in the general lighting. In general lighting, the use of inefficient LED, many of these equipment manufacturers suffering days.
From the lab to the factory
The following will explain how South Korea's Hexa Solution is solving these problems, and their core technology is the cavity sapphire substrate. South Korea's two research institutions conducted a feasibility study, laboratory-scale production shows that the combination of cavity design sapphire substrate LED than the pattern of sapphire substrate LED is better.
The process of producing a cavity sapphire substrate is robust and scalable (see Figure 1). The process begins with the photoresist pattern and the cylindrical photoresist is made into a dome shape by a reflow process. Subsequently, an 80 nm thick amorphous alumina layer was subjected to atomic layer deposition on all exposed surfaces at a temperature of 120C. Alumina is partially covered with sapphire, partially covered with photoresist.
The great advantage of this cavity substrate is their unique optical properties. They produce a strong interference, resulting in the naked eye can see a series of colors. Compared with the pattern sapphire, due to the strong diffraction of the cavity, in incandescent and fluorescent lighting will produce more vivid interference color (see Figure 3).
In addition, the transmission experiments show that the cavity sapphire in the wide wavelength range generated by the transmittance higher than the pattern of sapphire.
Time domain finite difference simulation shows that the high refractive index contrast cavity interacts with the upcoming plane wave very strongly. The results show that the cavity is effective in changing the direction of light propagation (see Figure 4).
Using a standard integrating sphere to measure optical power, the power generated by the LED in the cavity sapphire is usually significantly higher than the power generated on the patterned sapphire (see Figure 7). The spectrum of a single LED chip driven by a 240mA drive shows that the LED chips produced on the cavity sapphire provide peak emission at 468nm and produce an optical power that is 40% higher than the LED formed on the patterned sapphire. In the cavity sapphire produced on the main emission wavelength of 456nm and 462nm, the performance is also more than the pattern of sapphire LED, but the smaller (see Figure 8).