Light-emitting diodes (LEDs) were first commercially used in the 1960s as replacements for neon and incandescent lamps found in expensive laboratory and electronic test equipment. The cost of infrared and visible LEDs units was so steep back then that there was limited practical use. These days, the technology has found its way in diverse applications ranging from consumer electronics to industrial, automotive headlamps, traffic signals, billboards and aviation lighting.
The use of LEDs in lighting applications has soared over the past decade because of advantages such as longer lifetime and lower energy consumption compared to incandescent light sources. However, manufacturing costs continue to hamper its uptake. Gallium nitride (GaN) on sapphire substrate technology, developed in the early 1990s and provided the foundation for high-brightness blue LEDs, is currently the most commonly used production process. Gallium nitride on silicon (GaN-on-Si) is now emerging as a less costly alternative to sapphire.
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