Epitaxial layer capable of exceeding critical thickness

A semiconductor device comprising:

• a substrate made of a semiconductor material of a first conductivity type;
• a micro structure disposed on said substrate, said micro structure having irregular lattice constants at an upper surface of said micro structure and in an in-plane;
• a strained active layer disposed on said micro structure, said strained active layer being made of semiconductor material having on dislocations and containing strain;
• a clad layer formed on said strained active layer, said clad layer being made of semiconductor material of a second conductivity type, the semiconductor material of the second conductivity type having a lattice constant equivalent to a lattice constant of said substrate;
• and
• electrodes for allowing a current to flow between said substrate and said clad layer.

A semiconductor device comprising:

• a substrate having a principal surface exposing a first semiconductor material;
• an underlying layer disposed on the principal surface of said substrate, said underlying layer being made of a second semiconductor material containing in, the second semiconductor material having a lattice constant which lattice-mismatches a lattice constant of the first semiconductor material in a range of 1% or lower;
• and
• a strained active semiconductor layer disposed on said underlying layer, said strained active semiconductor layer being made of a third semiconductor material having a lattice constant different from a lattice constant of underlying semiconductor material and having no dislocations.

A semiconductor laser comprising:

• a substrate having a principal surface exposing a first semiconductor material of a first conductivity type;
• an underlying layer disposed on the principal surface of said substrate, said underlying layer including a second semiconductor layer of the first conductivity type containing In, the second semiconductor layer having a lattice constant which lattice-mismatches a lattice constant of the first semiconductor material in a range of 1% or lower;
• a lower spacer layer formed on said underlying layer and having a lattice constant which lattice-mismatches the lattice constant of the second semiconductor layer in a range of 1% or lower;
• a strained active semiconductor layer disposed on said lower spacer layer, said strained active semiconductor layer including a third semiconductor layer having a lattice constant different from lattice constants of the first semiconductor material and the second semiconductor layer, having no dislocations and being thicker than a critical film thickness determined by a Matthews-Blakeslee equation;
• an upper spacer layer formed on said strained semiconductor layer and having a lattice constant which lattice-mismatches the lattice constant of the second semiconductor layer in a range of 1% or lower;
• an intermediate layer formed on said upper spacer layer and including a fourth semiconductor layer of a second conductivity type opposite to the first conductivity type, the fourth semiconductor layer having a lattice constant which lattice-matches the lattice constant of the first semiconductor material in a range of 1% or lower;
• and
• electrodes for flowing current between said intermediate layer and said substrate.

A semiconductor laser comprising:

• a substrate made of a semiconductor material of a first conductivity type;
• an underlying layer of the first conductivity type disposes on said substrate, said underlying layer either having irregular lattice constants on an upper surface of said underlying layer and in an in-plane or containing In;
• a strained active layer disposed on said underlying layer, said strained active layer being made of semiconductor material having no dislocations and containing strain;
• a clad layer made of semiconductor material of a second conductivity type opposite to the first conductivity type and formed on said strained active layer, said clad layer having a lattice constant which lattice-mismatches a lattice constant of said substrate in a range of 1% or lower;
• and
• electrodes for flowing current between said substrate and said clad layer.