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材料和制造改进提高LED效率
从理论上说，制造高亮度LED很容易。只要粘在n型和p型半导体上，加上一个小的偏置电压，当光子流出时就往后退。然而，实际上，这些固态光源绝不简单。先进的材料和制造工艺结合在一起，生产出了十年前被认为是异想天开的奇异输出设备。
尽管他们生产出令人印象深刻的高效设备，但LED制造商并没有固步自封。领先的LED企业如Cree公司，欧司朗，和汉城半导体花费数百万美元在材料科学和制造技术，进一步提升产品的性能。
当代高亮度LED已经受益于先进的基板和制造技术，如碳化硅（SiC）和化学气相沉积（CVD），和明天的芯片将利用像图案化蓝宝石仍然渗透在实验室材料。本文将仔细研究这些材料和工艺，并评估它们对商业LED性能的影响。
Mind the band gap
Because the wavelength of the light emitted is a funcTIon of the energy band gap of the n- and p-doped semiconductor used to form the juncTIon， engineers are limited in their choice of materials for fabricaTIng LEDs. There is little point in selecTIng a semiconductor that emits photons that the eye cannot detect.
After many years of experimentation and hundreds of millions of research dollars， it turns out that Indium Gallium Nitride （InGaN） – a combination of Gallium Nitride （GaN） and Indium Nitride （InN） – is the best currently available semiconductor for high-brightness LEDs. The band gap of InGaN can be manipulated by altering the ratio of GaN to InN. The chips used at the heart of “white” LEDs， for example， emit photons in the 390 to 440 nanometer part of the spectrum （ultraviolet， violet-blue， and blue）1. These photons are then converted to white light by interaction with phosphor powder.
