HOT TECHNICAL PAPERS

In this section, we examine emerging science and technology knowledge domains that may someday intersect solid-state lighting. To do so, we used a citation analysis method similar to that pioneered by the Institute of Scientific Information (ISI). (For more information, see ISI's in-cites website ). The analysis below was conducted in August of 2004 and will be updated periodically. Based on citation analysis, 19 relevant articles emerged as "hot papers". We note that the ways in which emerging science and technology intersect with future engineering applications are difficult (if not impossible) to predict, so we will certainly have missed some SSL-relevant material. Nevertheless, these articles can give some useful perspective on some of the most exciting, current areas of science and technology that may someday be linked with solid-state lighting.

Results of Citation Analysis

The list of these papers, along with links to their abstracts, is shown in the table below. Nine articles are from the U.S., nine are from Asia (Taiwan, Japan and South Korea), and one is from Europe (Germany).

Major emerging themes with three or more articles each are:

·   Band structure and properties of InN and InGaN alloys (five articles). This is an especially important area, as InGaN alloys span the crucial red-yellow-green-blue wavelength spectrum, but emission in the red-yellow-green (and especially in the red-yellow) is very inefficient. These alloys are also relatively immature, and even their fundamental band structure properties are not well understood.

·   Light emitters with novel current injection (three articles). Current transport and injection is the fundamental first step preceding electron-hole recombination and light emission. Hence, device designs that can improve the efficiency of such transport and injection are of great current interest.

Major emerging themes with two articles each are:

·   Impurity-modified heterostructures and light emission (two articles). Impurities and dopants play an essential role not just in the electronic properties of semiconductors, but often in their optoelectronic properties as well. These articles explore the use of doping to engineer particular optoelectronic properties.

·   Non-polar AlGaInN heterostructures (two articles). This important area addresses the possibility of light emission from heterostructures in which electron-hole recombination is not slowed by a spatial separation caused by internal electric fields.

·   AlGaInN 0D and 1D nanostructures (two articles). It is well-known that randomly formed nanostructures are an essential reason for the relatively high efficiency of InGaN blue LEDs. It is possible that non-random, controlled nanostructures could ultimately lead to even higher efficiencies in the blue, and possibly at other wavelengths.

·   UV light emitters (two articles). One approach to solid-state lighting is the use of UV light emitters to excite multi-color phosphors. Hence, increasing the efficiency of currently-relatively-inefficient UV emission is an active and promising area.

Emerging themes with one article each are:

·   ZnO materials synthesis and properties (one article). There are semiconductor families other than the AlGaInN family that have the potential for the visible or near-UV light emission useful for solid-state lighting. ZnO-based materials are one of the more likely possibilities, but an understanding of their synthesis and properties is relatively immature.

·   Semi-insulating GaN (one article). AlGaInN alloys, being "ceramic-like" materials, are notoriously difficult to process, hence device architectures that benefit from independent control of electronic carrier flow and optical modes are difficult to realize. The process described in this article may enable such independent control.

·   Photon manipulation in nanostructures (one article). Light extraction from semiconductor LEDs is still a relatively inefficient process. Hence, the emerging area of photonic crystals, where periodic and aperiodic nanostructures are used to manipulate optical modes and photon transport, may be of great long-run potential benefit.

                                                            -- Analysis by Jeff Tsao, Sandia National Laboratories

The information presented in this section has been developed by Perspectives , a firm that specializes in technical and market intelligence, with assistance from Sandia National Labs. NOTE:  The provision of summaries and mention of specific manufacturers or products does not constitute an endorsement by Sandia National Laboratories or Perspectives; nor is the information presented warranted or guaranteed by either Sandia National Laboratories or Perspectives.