LED chip and package design and production trends

LED manufacturer Epistar presented their research results on a high voltage LED chip that can achieve 162Lm/W for cool white (5000k) LEDs.

The chip is described as a monolithically integrated, DC multi-array high voltage application LED chip. Epistar expects this product to become a mainstream product for general lighting.

The luminous efficiency of 162Lm/W was achieved by driving current of 20 mA and voltage of 47V, corresponding to power consumption of 0.94W. Under these conditions, the 45-mil chip can produce 152Lm.

Epistar said that HV-LEDs have lower power requirements and higher socket efficiency than traditional LEDs because of its powerful new high voltage chip design. According to the company, the flexibility of HV-LEDs to change voltage and current can simplify LED packaging and circuit design, thereby improving overall efficiency.

SMASH project progress

The SMASH project has published its second letter. The goal of SMASH is to achieve high efficiency and low cost devices by establishing a disruptive way to manufacture LEDs through nanostructured materials. These goals will be achieved through the epitaxial growth of LEDs composed of ultra-low defect nanostructured templates and the development of LED structures based on nanorod emission. These methods can have a significant impact on production costs because they allow the growth of large-area but low-cost substrates (such as silicon).

The most critical step is MOVPE. This was done by Osram Opto Semiconductor in close cooperation with the Technical University of Braunschweig.

The SMASH website and letter contain a summary of the 2010 International Workshop on Nitride Semiconductors (September 19-24, 2010).

Verticle Demonstrates First Hexagonal LED Chip

An article in Semiconductor Today states: Verticle, based in Dublin, California, USA, has unveiled what it claims is the first hexagonal LED chip. The honeycomb LED chip is a vertically structured, InGaN-based blue LED chip that is specifically designed for high-voltage applications. CEO Mike (MC) said that compared with traditional square or rectangular LED chips, a hexagonal chip will gain in cost, light output efficiency and beam profile.

Sumitomo Electric Develops 6-inch GaN Substrate

According to a Japanese magazine, Sumitomo Electric has developed the world's first 6-inch diameter GaN substrate for white LED applications. Previously, the company produced 2-inch GaN substrates for blue-violet lasers, which enabled the invention and production of Blu-ray DVD players. Sumitomo Electric has begun mass-producing 2-inch GaN substrates for white LEDs, while also developing larger diameter substrates.

The surface of the newly developed 6-inch substrate is a single-polarization c-plane. Sumitomo Electric is now working hard to mass-produce it and hopes that this material will be widely used in white LEDs and power devices.

Nanorod Arrays Produce Natural White LEDs

Researchers at National Tsing Hua University (Hsinchu, Taiwan) have developed a new recipe for phosphor-free white LEDs, according to a paper published in OptolQ. The pattern of GaN nanorods arrayed on a silicon (Si) substrate provides a template for growing stress-free InGaN/GaN heterostructure nanorods, a technique that can be used to eliminate piezoelectric polarization effects.

LED Packaging and Assembly

At the MEPTEC Semiconductor Packaging Roadmap Conference (held in Santa Clara, California in October 2010), ElectrolQ interviewed Jan Vardaman, president of TechSearch International. He said there is room for improvement in LED packaging and assembly.

In this interview with Debra Vogler, a senior technology editor, Vardaman discussed sapphire and SiC substrates, along with the various methods currently used by LED manufacturers. Substrate wafer size and LED production criteria were also discussed.

Blue Semipolar GaN LEDs

Researchers from the University of California, Santa Barbara (UCSB) and Mitsubishi Chemical Corporation (Ibaraki, Japan) have developed a new backside roughening technology for GaN-based blue LEDs. According to a paper on the OptolQ website, this technology allows GaN-based blue LEDs to be comparable in performance and production methods to wurtzite c-planar LEDs.