AlGaN-based ultraviolet light-emitting diodes grown on AlN epilayers

Abstract

AlGaN-based deep-ultraviolet light-emitting diode (LED) structures, which radiate light at 305 and 290nm, have been grown on sapphire substrates using an AlN epilayer template. The fabricated devices have a circular geometry to enhance current spreading and light extraction. Circular UV LEDs of different sizes have been characterized. It was found that smaller disk LEDs had higher saturation optical power densities but lower optical powers than the larger devices. This trade-off between power and power density is a result of a compromise between electrical and thermal resistance, as well as the current crowding effect (which is due to the low electrical conductivity of high aluminum composition n- and p-AlGaN layers). Disk UV LEDs should thus have a moderate size to best utilize both total optical power and power density. For 0.85mm×0.85mm interdigitated LEDs, a saturation optical power of 2.9mW (1.8mW) at 305nm (290nm) was also obtained under dc operation.

Mn2+-doped Ba2ZnS3 phosphor as a potential luminescent material for white LEDs

“…To solve these problems, one can use an ultraviolet LED chip as the excitation source, which is similar to fluorescent light tube. Recently much progress has been made for the emission efficiency of LED chips in the near UV-to-blue range [2][3][4]. The term "near UV" as used herein means UV radiation having wavelengths in the range from about 315 to about 410 nm.…”

Enhanced Optical Power of InGaN/GaN Light-Emitting Diode by AlGaN Interlayer and Electron Blocking Layer

“…As a result, electron overflow and insufficient hole injection can reduce the radiative recombination rate in InGaN/GaN MQWs [6]. A p-type Al x Ga 1−x N layer has been inserted between the p-type GaN MQWs as an electron blocking layer (EBL) to prevent electron overflow [7]- [9]. The Al composition of p-type Al x Ga 1−x N EBL should be increased to obtain an effective barrier height.…”

Orange emission enhancement by energy transfer in Sr3Al2O5Cl2:Ce3+, Eu2+ phosphor for solid-state lighting

“…Thus, the n-UV LEDs are expected to have a great application potential in the field of solidstate lighting. Recently much progress has been made for the emission efficiency of LED chips in the near-UV range [6][7][8]. Therefore, it is necessary to develop novel phosphor materials that are excitable in the near-UV range and emit in the visible range such that they may be used flexibly to design light sources having tunable properties, such as color temperature and color rendering index (CRI).…”