Sapphire Industry Watch – December 19

  • Rubicon’s interim president & CEO made permanent; VP – financial operations becomes CFO – Semiconductor Today: Rubicon Technology announced that its Board of Directors has appointed William Weissman to the permanent position of President and CEO. Weisman has been Interim CEO and President since September 17, 2014 and Chief Financial Officer since 2007. He has also been appointed a member of the Board of Directors.
  • Why LEDs Are Conquering Lighting – Popular Science: As the cost of LEDs continues to plummet and stricter efficiency standards are enforced, we are reaching a tipping point when it comes to LED conversion. LEDs are quickly becoming the preferred lighting source for a variety of applications, from home lighting to street lights.  Because they’re so efficient and highly programmable, LED adoption will continue to rise in the foreseeable future.
  • Christmas Lights Can Be Seen From Space By NASA Satellites– Huffington Post: The effect of holiday lights in cities and suburbs around the world is so powerful that the difference from normal lighting conditions can be detected from space. NASA satellite images show certain cities shine between 20 and 30 percent brighter during the holiday season and in the near future, satellites may even be able to differentiate between traditional lights and LEDs.
  • Virginia Beach switching to LED lights for roadways – PilotOnline.com: Virginia Beach will begin installing LED lighting technology to all new roads moving forward, with 180 LED street lights being installed on the newly expanded Princess Anne Road in January. Unlike the old-style lamps which glowed yellowish-orange, the new flat fixtures will illuminate the street with white light. The city expects to save hundreds of thousands of dollars by switching to LED lights.

Sapphire Industry Watch – December 12

  • Denmark laboratory shows off latest energy saving street lamps– CCTV America: The Danish Outdoor Lighting Lab is demonstrating the world’s most efficient outdoor lighting systems in a small industrial park just outside Copenhagen so that city planners can get a first-hand look at what is available for their municipalities.. All examples have Wi-Fi computer management systems and several have motion sensors and LEDs. These technologies bring enormous potential for energy savings, particularly in developing countries where it is essential to bring down the carbon footprint.
  • “Inspired Light” Combines Light Painting And Automotive Photography– Fstoppers:  World-renowned light painting photographer Patrick Rochon recently finalized a project with Infiniti where he photographed XQ70s in motion with multi-colored LED strips attached to them, making it appear as though the cars painted pictures. Precision drivers were hired to “light paint” with the vehicles, each of which had a total of 2,520 LEDs with output exceeding 30,000 lumens.
  • Nobel Prize winners reflect on difficulties faced in developing blue LED– The Asahi Shimbun: The three winners of this year’s Nobel Prize in Physics spoke at Stockholm University on December 8 about the difficulties they faced in the 1980s as they were developing the blue LED. They recalled that one of the biggest obstacles was creating crystals needed for the blue LED from gallium nitride. After years of trying to come up with the right material, the pure crystals were finally created in 1985.
  • Designers illuminate us on their winter wonders– The Japan Times: While Japanese lighting displays rarely include typical Christmas icons such as Santa or dancing snowmen, the illuminations are just as whimsical and often serve as a showcase for technological advances in the field of LEDs. These displays have become massive endeavors with corporate sponsors ranging from real estate companies to brands such as Hennessey Cognac. Architecture professor at Tokyo City University Shiego Kobayashi noted that the massive display of light lift people’s spirits and eases the coldness of the long winter nights.
  • LED market to grow at 17.9% from $46.4bn in 2014 to $105.5bn in 2019– Semiconductor Today: As the usability and efficiency of LEDs over traditional light bulbs has steadily increased over the last decade, the global market for high-brightness LEDs is expected to grow at a CAGR of 17.9% from nearly $46.4 billion in 2014 to $105.5 billion in 2019. LEDs for general illumination applications have the highest growth rate of any major segment.

The Many Sides of Sapphire

Sapphire substrates are used to grow semiconductor compounds, most commonly GaN for LEDs and other applications such as high temperature superconductors. They are also used to grow silicon for manufacturing microwave ICs, high-speed ICs and pressure transducers.

Sapphire is the single crystal form of aluminum oxide (Al2O3), and single crystals are made of identical building blocks, known as unit cells, which repeat themselves continuously and unbroken from edge to edge. This makes the atom arrangement of a sample highly organized and predictable. The crystal structure of sapphire is hexagonal/rhombohedral.

ShapeTo grow different material on sapphire with atom layer-to-layer precision requires atomic level agreement between the substrate and the material. These requirements are only satisfied along specific surfaces known as planes of the sapphire crystal.  Optical properties, hardness and thermal conductivity of sapphire also vary significantly by the orientation.

Based on application specifications, sapphire single crystal structure is divided into multiple planes. The planes most frequently used — c, a, m and r — are shown in the figure with respect to sapphire crystal axis directions. The atomic arrangement in each plane is unique and shown in the figures below with grey atoms representing aluminum and red atoms representing oxygen.

a-plane

a-plane

c-plane

c-plane

m-plane

m-plane

r-plane

r-plane

Sapphire Industry Watch – December 5

  • Orbital Sciences’ Third Mission to Space Station Ready to Educate & Inspire – Product Design & Development: Orbital Sciences’ latest mission to the International Space Station will transport a student research project that will test the effects of microgravity and light wavelength on plant growth, specifically pea shoots. Seeking to identify the best combinations of red and blue LED lights to grow the pea shoots in space, student researchers will analyze the plants’ mineral content upon return. The results could lead to more efficient crop production on Earth, especially in areas with limited resources.
  • Greener stadiums: Sports world sees the (LED) light – GreenBiz: As the cost curve continues to fall and technological advances continue to be made, sports stadiums have finally begun making the switch to LEDs. Though sports venues have been slow to adopt efficient lighting breakthroughs in the past, LED lighting systems have become preferred over metal halides since due to their low energy consumption and light production efficiency.
  • A Skokie Native’s Smart LED Light That Mimics the Sun Is a Hit on Kickstarter – ChicagoInno: Invented by a native of Skokie, Illinois, the Sunn Light is an LED light that changes color and brightness with the rhythm of the sun. The Sunn Light is designed to improve sleep and increase focus by helping adjust our internal clocks to the right time of day.
  • Let it glow! Father breaks world record with incredible Christmas display that uses 120kms of LED lights – Daily Mail Online: Australian David Richards breaks the Guinness World Record for largest Christmas LED light display by using 120km of lights and more than one million bulbs to decorate Canberra’s central business district. The extravagant light display, which has been nine months in the making, is done annually in an effort to raise vital funds for the SIDS and Kids charity.
  • Have you noticed a change in the Des Moines skyline? – KCCI 8 News: Not only is the 801 Grand in Downtown Des Moines the tallest building in Iowa, but thanks to the recent installation of LED lights, it is now the brightest. As part of a $284 million renovation, the entire downtown campus is receiving an outdoor lighting upgrade in order to light up the area more brightly and to save money.

Sapphire Substrate Advances Lead to Brighter LEDs at Lower Costs

As LED manufacturers relentlessly strive to produce greater light output at a lower cost, the most significant advance in cost per lumen in recent years has been the adoption of patterned sapphire substrates (PSS).

When a pattern is etched onto polished sapphire — the material used as a substrate in the vast majority of LED chips — total light extraction efficiency (LEE) can be increased by as much as 30 percent. This can happen in two different ways:

(1)    By encouraging lateral growth of the epitaxial layers, thereby reducing epitaxial defect density and increasing the light emission of the active quantum well layers

(2)    By reducing light loss, through creation of a photon scattering effect that allows more of the light generated to escape

Generally, the patterns consist of shapes — cones, domes, pyramids — created in a hexagonal pattern on the surface of the sapphire through dry plasma etching. Pattern features may be 0.65 to 2 microns in height, and the pitch (the distance between the centers of adjacent features) may be 1.5 to 3 microns.

SSL Design Blog Post Image

These pattern designs are developed independently by each of the LED manufacturers to meet the needs of their unique epitaxial recipes and are considered proprietary technology. Because of this, no standard library of patterns exists. The critical dimensions to increasing LEE include the shape and size of the pattern features and the aspect ratio — the ratio of height to width. Deeper patterns tend to be associated with greater LEE, but can be difficult to make if conditions are not well-controlled.

In addition to developing their PSS recipes in-house, LED manufacturers originally performed the patterning operations themselves. While most still conduct some of their patterning operations in-house, third-party patterning became more available in 2010 for two-inch wafers, and later four-inch wafers. It was then that LED companies had the option of outsourcing at least a portion of their patterning activity.

Concurrently with the development of patterned wafers, LED chip manufacturers have been slowly migrating to larger substrates for greater efficiency. Larger wafers provide several benefits, including:

  • Increased throughput for each reactor run, effectively increasing capacity without adding additional MOCVD reactors or additional floor space
  • Reduced edge loss
  • Reduced wafer handling

The yield for PSS at larger diameters is affected by the flatness of the wafer, and bowing of the wafer can cause inconsistent etching and lower yields.

So what’s next for PSS? Can we get even more luminous efficiency with this technology?

Nanoscale patterning has been extensively studied for its potential impact on light extraction efficiency due to both its significantly increased pattern density and its impact on internal quantum efficiency from the improvement of epitaxial quality. As we continue to test new patterns and sizes, like nanoscale patterning, it is clear that the industry hasn’t reached a wall in what is possible for light output. Further advances in PSS technology will provide improvements in light extraction efficiency, contributing to the continued market success of LED technology.