Nitride semiconductor device having a nitride semiconductor substrate and an indium containing active layer

A nitride semiconductor comprising:

• a nitride semiconductor substrate having a first surface and second surface;
• a nitride semiconductor structure having an indium-containing active layer, the nitride semiconductor structure having been grown on the first surface of the nitride semiconductor substrate;
• an n-side electrode formed on the second surface of the nitride semiconductor substrate;
• and
• a buffer layer in contact with the nitride semiconductor substrate, the buffer layer being a distorted superlattice structure formed by alternately stacking first and second nitride semiconductor layers having different compositions,
• wherein the nitride semiconductor structure is at least partially formed in a ridge at its top surface, and
• wherein the side surfaces of the nitride semiconductor structure is formed on or parallel to an M plane of the nitride semiconductor substrate.

A nitride semiconductor device comprising:

• a nitride semiconductor substrate having a first surface and second surface;
• a nitride semiconductor structure having an indium-containing active layer, the nitride semiconductor structure having been grown on the first surface of the nitride semiconductor substrate;
• and
• an n-side electrode formed on the second surface of the nitride semiconductor substrate,
• wherein the nitride semiconductor structure is at least partially formed in a ridge at its top surface,
• wherein the side surfaces of the nitride semiconductor structure is formed on or parallel to an M plane of the nitride semiconductor substrate, and
• wherein the nitride semiconductor substrate is doped with an n-type impurity such that the n-type impurity concentration has a gradient, wherein the gradient from said first surface to said second surface is from lesser concentration to greater concentration.