▎ 摘　　要

NOVELTY - A UV light-emitting diode comprises: n-type semiconductor layer (300); active layer (400) disposed on n-type semiconductor layer; p-type semiconductor layer (500) formed of p-type aluminum gallium nitride, disposed on active layer; and p-type graphene layer (600) formed of graphene doped with p-type dopant, disposed on p-type semiconductor layer. USE - As UV light-emitting diode (claimed) useful in displays, optical communications, automobiles, and general illumination. ADVANTAGE - The UV light-emitting diode has improved light-emission efficiency via maximization of UV transmittance. The p-type graphene layer in UV light-emitting diode lowers contact resistance with p-type semiconductor layer and maximizes UV transmittance. The contact resistance between p-type graphene layer and p-type semiconductor layer is less than or equal to 10-4 ohm/cm2. The p-type graphene layer has transmittance of greater than or equal to 90% with respect to UV light with wavelength of 280 nm. In comparative example, p-GaN layer used as p-type contact layer lowers contact resistance but sharply reduces UV light-emission efficiency because it absorbs much UV light e.g. when p-GaN is used to form p-type contact layer it has UV light transmittance which rapidly drops as compared to visible light transmittance. However, p-type graphene layer used instead of p-GaN layer reduces contact resistance and still increases UV light-emission efficiency. Since doping of graphene with p-type dopant enables adjustment of work function of p-type graphene layer, contact resistance with p-type semiconductor layer formed of AlGaN can be minimized. The graphene quantum dot has large number of electrons, but number of free electrons included may be limited to 1-100. In this case, since energy levels of electrons are discontinuously restricted, graphene quantum dot may have different electrical and optical characteristics from graphene sheet that forms continuous band. Since graphene quantum dot has different energy levels according to different sizes of graphene quantum dot, size of graphene quantum dot may be adjusted to control bandgap. Thus wavelength of emitted light may be controlled by simply controlling sizes of graphene quantum dot. In addition, since each graphene quantum dot has very high state densities of electrons and holes on bandgap edge compared to graphene sheet, many excited electrons and holes are combined with one another, thus enable increase of light-emission efficiency. DETAILED DESCRIPTION - A UV light-emitting diode comprises: n-type semiconductor layer (300); active layer (400) disposed on n-type semiconductor layer; p-type semiconductor layer (500) formed of p-type aluminum gallium nitride (AlGaN), disposed on active layer; and p-type graphene layer (600) formed of graphene doped with p-type dopant, disposed on p-type semiconductor layer. The p-type graphene layer is in the form of p-type graphene quantum dot layer. The upper structure of p-type graphene layer has nanostructure. The cross-section of nanostructure has triangular or rectangular unit structure. The p-type dopant of p-type graphene layer is HNO3 and/or AuCl3. The UV light-emitting diode further comprises reflective layer (800) disposed on p-type graphene layer, where reflective layer is configured to reflect UV light emitted from active layer, and material used to form reflective layer comprises metal; and p-type contact layer disposed between p-type semiconductor layer and p-type graphene layer, comprises p-GaN, and has thickness of less than or equal to 20 nm. The active layer emits light having wavelength of 200-400 nm. DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional views of UV light-emitting diode including reflective layer. Substrate (100) Buffer layer (200) N-type semiconductor layer (300) Active layer (400) P-type semiconductor layer (500) P-type graphene layer (600) N-type electrode (610) Reflective layer (800)