the superlattice structure 110 is ingan however the superlattice structure 110 can also be composed of one to two sets of wide bandgap semiconductor material layer narrow bandgap semiconductor material layer and wide bandgap semiconductor material layer stacked in sequence wherein the material of the wide bandgap semiconductor material layer and the narrow bandgap semiconductor material layer can be such as p type doping nitride semiconductor and the material of the two wide bandgap semiconductor material layers is gan preferably and the material of the narrow bandgap semiconductor material layer located between the two wide bandgap semiconductor material layers is ingan preferably furthermore the thickness of the wide bandgap semiconductor material layer of the superlattice structure 110 is preferably less than 100 u00e5 and the thickness of the narrow bandgap semiconductor material layer of the superlattice structure 110 is preferably less than 500 u00e5 preferably besides the top layer of the superlattice structure 110 is a wide bandgap semiconductor material layer preferably and the thickness of the wide bandgap semiconductor material layer the top layer of the superlattice structure 110 is less than 50 u00e5 preferably the superlattice structure 110 can provide tunneling contact for carriers so that the forward voltage difference can be designed and kept constant to obtain a low forward voltage additionally the transparent conductive layer 112 can have good contact with the superlattice structure 110 without relying.