AlGaN deep ultraviolet light-emitting diodes (DUV LEDs) have a wide variety of potential applications, including uses for sterilization, water purification, and UV curing and in the medical and biochemistry fields. However, the wall-plug efficiency (WPE) of AlGaN DUV LEDs remains below values. We have developed crystal growth techniques for wide-bandgap AlN and AlGaN and, using these techniques, fabricated DUV LEDs in the 220–350 nm-band. Considerable increases in the internal quantum efficiency (IQE) of AlGaN quantum wells (QW) were achieved by developing low-threading dislocation density (TDD) AlN grown on sapphire substrates. The electron injection efficiency (EIE) was substantially increased by introducing a multi-quantum barrier (MQB) as an electron-blocking layer (EBL). The light-extraction efficiency (LEE) was also improved by using a transparent p-AlGaN contact layer, a highly reflective (HR) p-type electrode, and an AlN template fabricated on a patterned sapphire substrate (PSS). Further improvements were made by implementing a reflective photonic crystal (PhC) p-contact layer. We demonstrated a record external quantum efficiency (EQE) of 20.3% for an AlGaN UVC-LED.
Part of the book: Light-Emitting Diode