Application of Quaternary AlInGaN- Based Alloys for Light Emission Devices

Excellent progress has been made during the past few years in the growth of III-nitride materials and devices. Today, one of the most important application of novel optoelectronic devices is the design and engineering of light-emitting diodes (LEDs) working from ultraviolet (UV) through infrared (IR), thus covering the whole visible spectrum. Since the pioneer works of Nakamura et al. at Nichia Corporation in 1993 (Nakamura et al. (1995)) when the blue LEDs and pure green LEDs were invented, an enormous progress in this field was observed which has been reviewed by several authors (Ambacher (1998); Nakamura et. al. (2000)). The rapid advances in the hetero-epitaxy of the group-III nitrides (Fernández-Garrido et al. (2008); Kemper et al. (2011); Suihkonen et al. (2008)) have facilitated the production of new devices, including blue and UV LEDs and lasers, high temperature and high power electronics, visible-blind photodetectors and field-emitter structures (Hirayama (2005); Hirayama et al. (2010); Tschumak et al. (2010); Xie et al. (2007); Zhu et al. (2007)). There has been recent interest in the AlxIn1−x−yGayN quaternary alloys due to potential application in UV LEDs and UV-blue laser diodes (LDs) once they present high brightness, high quantum efficiency, high flexibility, long-lifetime, and low power consumption (Fu et al. (2011); Hirayama (2005); Kim et al. (2003); Knauer et al. (2008); Liu et al. (2011); Park et al. (2008); Zhmakin (2011); Zhu et al. (2007)). The availability of the quaternary alloy offers an extra degree of freedom which allows the independent control of the band gap and lattice constant. Another interesting feature of the AlGaInN alloy is that it gives rise to higher emission intensities than the ternary AlGaN alloy with the absence of In (Hirayama (2005); Wang et al. (2007)). An important issue is related to white light emission, which can be obtained by mixing emissions in different wavelengths with appropriate intensities (Roberts (1997); Rodrigues et al. (2007); Xiao et al. (2004)). Highly conductive p-type III-nitride layers are of crucial importance, in particular, for the production of LEDs. Although the control of p-doping in these materials is still subject of discussion, remarkable progress has been achieved (Hirayama (2005); Zhang et al. (2011)) and 14