ABSTRACT
This chapter gives a brief overview of the field of visible light-emitting diodes (LEDs). Light-emitting semiconductor diodes are light sources that were developed in the last few decades. The basic function of an LED is to generate light following the injection of an electrical current into the semiconductor material. When designing LEDs, it is very important to consider surface recombination. Carrier injection into the active region of the device should take place several diffusion lengths away from any surface. From a fabrication point of view, planar LED structures with the shape of a rectangular parallelepiped are favorable. The resonant-cavity LED (RCLED) consists of a light-emitting active region between two Bragg mirrors which form an optical resonator. RCLEDs have been fabricated mostly for the infrared spectral range, often with the intention to use them as efficient light source in fiber communication systems.
