Patent ID: 7042019

Claim:
A GaN-based MQW LED structure, comprising: a substrate made of a material selected from the group consisting of sapphire, 6H-SiC, 4H-SiC, Si, ZnO, GaAs, MgAl 2 O 4 , and an oxide monocrystalline having a lattice constant compatible with that of nitride semiconductors; a buffer layer made of Al a Ga b I 1-a-b N (0≦a,b<1, a+b≦1) having a specific composition located on top of an upper side of said substrate; an n-type contact layer located on top of said buffer layer; an active layer made of InGaN located on top of a part of said n-type contact layer's upper surface; a negative electrode located on top of another part of said n-type contact layer's upper surface not covered by said active layer; a p-type cladding layer made of Mg-doped Al 1-c-d Ga c In d N (0≦c,d<1, c+d≦1) having a specific composition located on top of said active layer; a p-type contact layer made of Mg-doped Al 1-e-f Ga e In f N (0≦e,f<1, e+f≦1) having a specific composition located on top of said p-type cladding layer; and a positive electrode located on top of a part of said p-type contact layer's upper surface, wherein said n-type contact layer has a superlattice structure formed by a first number of first base layers made of an n-type group III nitride, and a second number of second base layers made of another n-type group III nitride, alternately stacked on top of each other, said second base layers have wider band gaps than those of said first base layers, a bottommost base layer of said n-type contact layer is selected from the group consisting of said first base layer and said second base layer, and a topmost base layer is selected from the group consisting of said first base layer and said second base layer; and wherein each or said first base layers is made of In- and Si-codoped GaN having a doping density independent of other base layers, and each of said second base layers is made of In- and Si-codoped Al 1-h Ga h N (0<h<1) having specific composition and doping density independent of other base layers.