Review—Visible LEDs: More than Efficient Light

The lighting sector has seen a tremendous technology revolution in the recent few decades. This process has been fueled by light emitting diodes (LEDs), when group-III nitride materials became available for semiconductor devices by groundbreaking technological discovery of p-type conductivity in gallium nitride (GaN). Ever since this Nobel prize winning discovery, the race of improving the efficiency and the efficacy of visible LEDs has been the dominant driving force, enabled by novel designs and processes to exploit novel materials, to improve material quality, electrical and thermal resistance, light extraction and beam shaping. Technology trends like miniaturization and integration of electronics and photonics have led LED markets to expand to a variety of novel application fields, such as illumination, sensing, healthcare and visualization, that are far beyond the traditional general lighting market. Integration of LEDs and other electronic devices like CMOS transistor or photodiodes adds novel functionalities in the smallest dimensions.