Metamorphic long wavelength high-speed photodiode

A metamorphic device grown on a substrate, the metamorphic device comprising:

• a substrate structure formed on the substrate, the substrate structure comprising:
• a buffer layer formed over the substrate, the buffer layer having a lattice constant that matches a lattice constant of the substrate;
• a first grading layer formed over the buffer layer, the first grading region ramping the lattice constant past a desired lattice constant;
• an intermediate layer formed over the first grading region;
• a second grading layer formed over the intermediate layer, the second grading region reversing the lattice constant back to the desired lattice constant;
• and
• a strained layer superlattice having one or more strained layers, each of the strained layers having a thickness less than a critical thickness;
• and
• a semiconductor device formed on the substrate structure.

In a system where a semiconductor device has a lattice constant that results in dislocations in the semiconductor device when formed on a particular substrate, a semiconductor structure grown on the substrate that enables the semiconductor device to be grown over the substrate, the semiconductor structure comprising:

• a first graded layer formed over the substrate, the first graded layer ramping a lattice constant of the substrate past a desired lattice constant;
• a second graded layer formed over the first graded layer, the second graded layer ramping the lattice constant back to the desired lattice constant, wherein at least the first graded layer and the second graded layer are annealed to isolate dislocated regions in at least the first graded layer and the second graded layer;
• and
• a strained layer superlattice formed over the second graded layer, wherein the semiconductor device is formed over the strained layer superlattice.