LED chips are a core component in the LED industry. There are currently many domestic and international LED chip manufacturers in China, but there currently are no categorization standards, according to a report by Chinese-language LEDtimes.cc. Comparison of chip technologies show foreign companies are more innovative, while Chinese manufacturers are still focused on production volume.
The LED chip sector can be segmented into power, color, shape, and even voltage. There are low, mid, and high power LED chips. Chips also come in red, green, and blue, while shapes generally come in squares or circles. Voltage wise, there is low voltage and high voltage DC chips.
Substrate material and epiwafer growth technologies are essential to chip development
At the moment, the key to LED chip technology development lies in substrate material and epiwafer growth technologies. In addition to common sapphire and silicon carbide (SiC) substrates in the LED industry, zinc oxide (ZnO), gallium nitride (GaN) and other materials have also become a major research focus in the LED chip industry. Most companies on the market currently employ sapphire or SiC substrates in epitaxal growth to make wideband gap semiconductor GaN. However, the two substrates are very costly, with large international manufacturers completely monopolizing the sapphire and SiC markets. In contrast, Si substrates cost less and can be made into larger substrates. By raising MOCVD utilization rates, crystal yield rates are also increased. Therefore, Chinese LED manufacturers aiming to penetrate international patent barriers should form partnerships with research institutes to develop Si substrates.
Still LED chip manufacturers are faced with the technology challenge of making high quality GaN-on-Si substrates in large volumes. The physical property mismatch between the two materials, especially in the lattice constant and coefficient of thermal expansion (CTE), can result in flawed products with high density and cracks. These technological issues are obstacles that have long plagued chip developments.
There is no doubt that sapphire and SiC will continue to be main substrate materials for the time being, but Si substrates developments has become the emerging LED chip sector trend. In price war stricken China, Si substrates have higher cost and price advantages. Si substrates not only can reduce crystal size in semiconductors, it can also remove etching procedure in GaN epiwafers. In addition, since Si is not as hard as sapphire and SiC, it can cut processing costs.
The LED industry is mainly focused in 2-inch or 4-inch sapphire substrates, manufacturers could save up to 75 percent raw material costs if GaN-on-Si technology was implemented instead. Japan’s Sanken Electric Co. estimates utilizing silicon substrates in the production of large sized GaN-based LEDs can lower manufacture costs by 90% compared to sapphire and SiC substrates.
Huge contrast between Chinese and international manufacturers LED chip technology
International LED chip manufacturers including Osram, U.S. manufacturer Bridgelux, SAMCO from Japan and other top manufacturers have already acquired technological breakthroughs in large-sized GaN-on-Si substrates for LED applications. Philips Lighting, Korean manufacturer Samsung and LG, Toshiba and other leading manufacturers have also initiated GaN-on-Si LED research trend. In 2011, Bridgelux developed an GaN LED with high luminous efficacy on an 8-inch Si substrate that matched top sapphire or SiC LED components efficacy of 160 lm/W. In the following year, Osram successfully developed a 6-inch GaN-on-Si LED
In comparison, China’s LED chip manufacturers major technological breakthrough has mainly been raising production capacity, and growing large-sized sapphire crystals. Lattice Power has been the only Chinese manufacturer to successfully mass produce high power 2-inch GaN-on-Si LED chips in 2011. Other Chinese chip manufacturers research have failed to reach significant breakthroughs in GaN-on-Si substrate technology. Chinese manufacturers are still focused on technologies covering raising production capacity, sapphire substrate, and wafer growth. Top Chinese LED chip manufacturers have made progress in production capacity, such as San’an Opto, Elec-Tech International (ETI) and Tsinghua Tongfang.
