This Small Business Innovation Program (SBIR) Phase I project aims to develop a new high brightness light engine platform by monolithically integrating high performance silicon transistors with compound semiconductor optoelectronic materials. Dense arrays of light emitting diodes (LEDs) have been previously fabricated to show the opportunity of using such arrays in microdisplay and projection concepts. However, without active control circuits, the ultimate brightness and resolution are limited. The technology developed in this SBIR uniquely allows for the fabrication of LED arrays with integrated control circuits on a single substrate enabling a light engine platform with high peak brightness (20,000,000 cd/m2), high dynamic range (from low light to outdoor sunlight), and high efficiency (80 lm/W). Prototype LED arrays have been fabricated, and the next step to realize this platform is the development of silicon circuitry to directly control the LED arrays. The anticipated results of this SBIR Phase I project are a low-temperature thin-film transistor fabrication process compatible with the LED arrays, appropriately scaled transistors, models of device performance and uniformity, and fully developed control circuits that will enable commercial demonstration devices.
The broader impact/commercial potential of this project is the development of a light engine with a power efficiency, brightness, cost, and form factor unavailable in incumbent systems. In particular, three markets are identified where this technology significant advantages over current technologies, the $200 million microdisplay market, the $490 million pico-projector market, and the $2 billion projector market. This light engine platform offers a small form factor, long lifetime, environmental robustness, and high energy efficiency, and the high brightness required for sunlight readability. These features are necessary to create truly ubiquitous display devices and enable new see-through augmented reality experiences or smaller, more integrated projectors, not possible with current technologies. Commercialization of this device will impact all of these areas and enable a range of new downstream applications including other non-display industries, such as, 3D scanning and novel user interfaces.
This Small Business Innovation Research Phase I project investigated the development of a high brightness microdisplay platform based on an integration of light emitting diodes (LEDs) and silicon technology. When fully developed, Lumiode’s technology can outperform current display technologies in nearly every figure of merit: brightness, efficiency, and contrast ratio. This is made possible by monolithically integrating an array of LEDs with active thin-film silicon circuitry. With the combined advantages of high brightness LEDs and high performance thin-film silicon transistors for pixel control, we can build microdisplays for see-through head-mounted applications, projection applications, or head-up display applications. Our display is an emissvie display; light is generated at each pixel only where and when required. Most display technologies start with a bright, unpatterned light source, such as a gas discharge lamp, a high brightness LED, or a high power laser. To generate an image, a spatial light modulator, such as liquid crystal display (LCD), liquid crystal on silicon (LCoS), or digital micromirror device (DMD), is required. In all of these technologies the light source is always on at maximum brightness regardless of the image being shown. In addition, these displays require complex optical components to create the optical path for the image. Our emissive microdisplay platform reduces the optical components and makes our display 5-10X more efficient, which translates to additional power savings, a brighter image, and a smaller device size. The outcome of this project is an important commercialization milestone by demonstrating an improved transistor fabrication process at temperatures compatible with compound semiconductor substrates. The new fabrication process also introduced an improved dopant implantation and activation process, reduced contact resistance, and replaced the previously used polymer gate dielectric with an industry standard thin-film gate dielectric. These improvements are the first step toward developing a robust, repeatable, and scalable fabrication process that can leverage the capabilities of commercial fabrication sources. Proof-of-concept, drive and logic circuits were designed and simulated using standard models of thin-film silicon transistors. Using the results from this project, Lumiode is designing, building, and testing devices towards the first commercial product.
