1. Overview of the current overall technological status of silicon based LEDs

The growth of GaN materials on silicon substrates faces two major technical challenges. Firstly, a lattice mismatch of up to 17% between the silicon substrate and GaN results in a higher dislocation density inside the GaN material, which affects the luminescence efficiency; Secondly, there is a thermal mismatch of up to 54% between the silicon substrate and GaN, which makes GaN films prone to cracking after high-temperature growth and dropping to room temperature, affecting production yield. Therefore, the growth of the buffer layer between the silicon substrate and GaN thin film is extremely important. The buffer layer plays a role in reducing the dislocation density inside GaN and alleviating GaN cracking. To a large extent, the technical level of the buffer layer determines the internal quantum efficiency and production yield of LED, which is the focus and difficulty of silicon-based LED. As of now, with significant investment in research and development from both the industry and academia, this technological challenge has been basically overcome.

The silicon substrate strongly absorbs visible light, so the GaN film must be transferred to another substrate. Before transfer, a high reflectivity reflector is inserted between the GaN film and the other substrate to prevent the light emitted by the GaN from being absorbed by the substrate. The LED structure after substrate transfer is known in the industry as a Thin Film chip. Thin film chips have advantages over traditional formal structure chips in terms of current diffusion, thermal conductivity, and spot uniformity.

2. Overview of the current overall application status and market overview of silicon substrate LEDs

Silicon based LEDs have a vertical structure, uniform current distribution, and fast diffusion, making them suitable for high-power applications. Due to its single-sided light output, good directionality, and good light quality, it is particularly suitable for mobile lighting such as automotive lighting, searchlights, mining lamps, mobile phone flash lights, and high-end lighting fields with high light quality requirements.

The technology and process of Jingneng Optoelectronics silicon substrate LED have become mature. On the basis of continuing to maintain leading advantages in the field of silicon substrate blue light LED chips, our products continue to extend to lighting fields that require directional light and high-quality output, such as white light LED chips with higher performance and added value, LED mobile phone flash lights, LED car headlights, LED street lights, LED backlight, etc., gradually establishing the advantageous position of silicon substrate LED chips in the segmented industry.

3. Development trend prediction of silicon substrate LED

Improving light efficiency, reducing costs or cost-effectiveness is an eternal theme in the LED industry. Silicon substrate thin film chips must be packaged before they can be applied, and the cost of packaging accounts for a large part of the LED application cost. Skip traditional packaging and directly package the components on the wafer. In other words, chip scale packaging (CSP) on the wafer can skip the packaging end and directly enter the application end from the chip end, further reducing the application cost of LED. CSP is one of the prospects for GaN based LEDs on silicon. International companies such as Toshiba and Samsung have reported using silicon based LEDs for CSP, and it is believed that related products will soon be available in the market.

In recent years, another hot spot in the LED industry is Micro LED, also known as micrometer level LED. The size of Micro LEDs ranges from a few micrometers to tens of micrometers, almost on the same level as the thickness of GaN thin films grown by epitaxy. At the micrometer scale, GaN materials can be directly made into vertically structured GaNLED without the need for support. That is to say, in the process of preparing Micro LEDs, the substrate for growing GaN must be removed. A natural advantage of silicon based LEDs is that the silicon substrate can be removed by chemical wet etching alone, without any impact on the GaN material during the removal process, ensuring yield and reliability. From this perspective, silicon substrate LED technology is bound to have a place in the field of Micro LEDs.