Group III nitride semiconductor light-emitting device

A Group III nitride semiconductor light-emitting device comprising:

• a substrate;
• an n-type layer side contact layer consisting of GaN doped with Si in a concentration of 5×1018/cm3 or more;
• an ESD layer for improving electrostatic breakdown voltage formed on and in contact with the n-type layer side contact layer;
• an n-type layer side superlattice layer formed on and in contact with the ESD layer;
• a light-emitting layer formed on and in contact with the n-type layer side superlattice layer;
• a p-type layer side cladding layer formed on and in contact with the light-emitting layer;
• a p-type layer side contact layer formed on and in contact with the p-type layer side cladding layer, each of the layers being formed of a Group III nitride semiconductor;
• an n-electrode formed on an exposed area of the n-type layer side contact layer;
• and
• a p-electrode formed on the p-type layer side contact layer;
• wherein the n-type layer side superlattice layer has a layered structure of an InzGa1-zN (0<z<1) layer having a constant composition ratio over the entire cycles and a GaN layer repeatedly deposited;
• and
• wherein the ESD layer comprises at least four layers of a first n-GaN layer doped with Si and directly contacted with the n-type layer side superlattice layer, an electron injection adjusting layer as a single layer consisting of an undoped AlxGayN (0<x<1, 0<y<1) layer and directly contacted with the first n-GaN layer, an undoped GaN layer directly contacted with the electron injection adjusting layer, and a second n-GaN layer doped with Si and directly contacted with the undoped GaN layer, the electron injection adjusting layer having an electron level of the bottom of conduction band higher than that of any other layers constituting the ESD layer and the n-type layer side contact layer, and having a thickness of 5 Å to 30 Å and an Al composition ratio x of 0.15 to 0.5, and
• wherein the first n-GaN layer has a thickness of 25 nm to 50 nm and a Si concentration of 1×1018/cm3 to 10×1018/cm3, the undoped GaN layer has a thickness of 50 nm to 500 nm, the second n-GaN layer has a thickness of 25 nm to 50 nm and a Si concentration of 1×1018/cm3 to 10×1018/cm3, and the second n-GaN layer has a thickness of 25 nm to 50 nm and a Si concentration of 1×1018/cm3 to 10×1018/cm3, and
• wherein an interface between the undoped GaN layer and the electron injection adjusting layer has a V pit with a diameter of 20 nm to 300 nm and a density of 1×108/cm2 or more originated from threading dislocation, and
• wherein the electron level of the bottom of conduction band of the electron injection adjusting layer is higher in operation state than the highest electron level of the bottom of conduction band of the p-type layer side cladding layer, and
• wherein the Al composition ratio x and thickness of the electron injection adjusting layer are adjusted so as to achieve a maximum light output.