Realization of 340-nm-Band High-Output-Power (>7 mW) InAlGaN Quantum Well Ultraviolet Light-Emitting Diode with p-Type InAlGaN

We have demonstrated 340-nm-band high-output-power InAlGaN quantum well (QW) ultraviolet (UV) light-emitting diodes (LEDs) under room temperature (RT) continuous wave (CW) operation, which were deposited on sapphire (0001) substrates by low-pressure metal–organic chemical vapor deposition (LP-MOCVD). The high-output-power UV LEDs were achieved by introducing p-type InAlGaN layers in order to obtain a high hole concentration and by optimizing the band lineup to suppress electron overflow. The output power of a UV-LED with p-InAlGaN layers was about 4.7 times larger than that of an equivalent structure containing p-AlGaN. We obtained a significant increase in output power by controlling the barrier height of the electron-blocking layer (EBL) and the depth of the quantum wells. We also obtained a marked increase in UV output power by introducing a low-threading-dislocation-density (TDD) AlN buffer layer. The maximum output power and external quantum efficiency (EQE) of LEDs containing p-InAlGaN layers were 8.4 mW and 0.9%, respectively, at an emission wavelength of 346 nm under room temperature (RT) CW operation.