ABSTRACT
Group III-based nitrides were identied as a potential material for light emission by Maruska and Tietjen in 1969 [1], by Pankove et al. in 1971 [2], and in later years by Akasaki et al. [3]. The workers investigated the properties of light-emitting diodes (LEDs) made of GaN. As the bandgap of GaN is ~3.4 eV, it is useful for emission in the ultraviolet (UV) region of the EM spectrum. The growth of single crystals of GaN and observation of the rst optically pumped stimulated emission were reported by Dingle et al. in 1971 [4]. After this, the progress in realizing electrically injected devices such as LEDs and laser diodes (LDs) became quite slow for various reasons, as will be discussed in this chapter. The real progress started in the 1990s [5,6], and since then there has been phenomenal growth in the area of nitride-based optoelectronic and electronic devices. Many devices have been commercialized and employed in day-to-day life. At present, the market for nitride-based devices and products is at the level of several billion dollars.
