Light revolution

“ LED there be light.” THE above could well be the words of Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, whose path-breaking invention of blue light-emitting diodes enabled the creation of white light in a new way and opened the way for the development of a new energy-efficient and environment-friendly light source. The older incandescent and fluorescent light sources are fast giving way to the LED-based white light sources in homes, shops and offices though cost still remains a major factor, and LEDs already form the basis for most of the electronic devices we use—mobile phones, tablets, laptops, computer monitors, television sets, car dashboards and luminous advertising billboards—in which they are the backlighting sources that shine light on their liquid crystal display systems. Around the same time, different researchers were making use of another III-V semiconductor, GaP—which, however, is only an indirect bandgap material—to develop LEDs that emitted light of different wavelengths ranging from red to green. There was improvement in the growth of GaN crystals with the development in the 1960s of a more efficient technique called Hybrid Vapour Phase Epitaxy, which laboratories in the United States, Europe and Japan began to use with the aim of developing blue LEDs with GaN, but material problems persisted and were extremely difficult to overcome.