One thing true in the semiconductor industry is that, when a problem is well-defined, the solution will be at hand shortly. A few years ago, the LED sector of the semiconductor industry turned its attention to the problem known as solid-state lighting. At that time, the conventional wisdom was that solid-state lighting would be about 10 years away. However, unprecedented progress in the past 16 months has reduced that time estimate to five years, and these advances have created an entirely new category of LED devices known as “lighting class” (Table 1).

Sixteen months ago, the brightest white-light LED that could be purchased commercially was around 50 lm at 350 mA, but advances in LED chip architecture have enabled the birth of lighting-class LEDs and have doubled the prior light output. This has been a critical enabler for outdoor lighting, because large arrays of individual LEDs are required to yield light output that is equivalent to that of conventional high-intensity discharge lamps. For example, with the older technology, an array of more than 200 LEDs would have been required to generate the same amount of light as a 175-W metal halide lamp. Arrays of LEDs of this size present a complicated electrical, thermal and mechanical design challenge and pose many difficulties in the field in terms of size, weight and wind resistance. Today, that same array would contain fewer than 100 LEDs, and the size, form factor and cost have scaled downward at the same rate that the brightness has scaled upward...

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