Mid-infrared light-emitting diodes

There are many applications for light-emitting diodes (LEDs) that can operate in the mid-infrared spectral range. However, the efficiency of these devices at room temperature is limited by competing nonradiative recombination mechanisms, inadequate carrier confinement, and insufficient optical extraction. Earlier devices based on bulk materials and heterojunctions have been quite successful to date, leading to some commercialization, but several new designs containing quantum structures for the active region have since been proposed and are being studied. Similarly, there is growing interest in using more cost-effective substrates requiring the development of metamorphic buffer layers as well as resonant cavity structures to increase optical extraction. An overview of the current status of mid-infrared LED technology is given here together with a brief summary of some recent developments.