Process for making a mesa GaInAsP/InP distributed feedback laser

The method of forming a DFB laser heterojunction device having alternate layers of semiconductor material with at least a first layer of one type conductivity, a second layer and a third layer of opposite conductivity comprising the steps of:

• (a) selectively etching only the third material until a mesa of third material is formed over the second layer and a surface of second layer material is exposed on two sides of said mesa;
• (b) selectively etching only the second layer material at the exposed surfaces until two undercut regions are formed under the mesa with a layer of second material therebetween which is exposed on two sides;
• and
• (c) filling in the undercut region with material from said mesa and first layer sufficient to bury the exposed portions of said second layer material;
• (d) forming a DFB grating structure on an exposed surface of one of the first or third layers adjacent the buried second layer.

A method of forming a double heterostructure distributed feedback type laser comprising:

• (a) forming a first body of semiconductor material having a major surface and a first type conductivity;
• (b) forming a second body in the shape of a mesa of semiconductor material having a conductivity opposite said first type conductivity, said second body having an external plateau surface and an adjacent surface opposite said plateau surface;
• (c) embedding a strip of active semiconductor material of narrower bandgap than the bandgap of the first and second bodies between said first and second bodies;
• (d) forming a periodic structure in the plateau of the second body extending in parallel proximity with the strip of active semiconductor material;
• (e) forming at least one ohmic contact strip on said plateau adjacent the periodic structure;
• and
• (f) forming contact means on said first body.

A method for forming a distributed feedback type laser comprising:

• (a) forming a first body of semiconductor material having a major surface and a first type conductivity;
• (b) forming a second body in the shape of a mesa with an external plateau surface and formed of semiconductor material of conductivity opposite said first type conductivity and having a major surface adjacent to the major surface of said first body;
• (c) embedding a strip of active semiconductor material between said two bodies and extending along the major surfaces;
• (d) forming a periodic structure in said plateau surface adjacent said strip;
• said structure comprising corrugations extending into said surface of sufficient depth such that light waves travelling along the region of the active layer interact with proximate portions of the corrugations but not the remote portions;
• (e) forming ohmic contact means on the remote portions of the corrugations.

A method of forming a laser comprising:

• (a) forming a first body of semiconductor material having a first type conductivity;
• (b) forming a second body of semiconductor material of opposite type conductivity to the first type;
• (c) forming a strip of active lasing material between and embedded in said first and second bodies, said strip having a pair of side walls extending between said bodies;
• (d) forming a periodic structure on at least one side wall of said embedded strip;
• and
• (e) forming contact means on said first and second body.

The method of forming a surface emitting laser with distributed feedback comprising:

• (a) forming a first body of semiconductor material having a first type conductivity and a major surface;
• (b) forming a second body of semiconductor material of opposite type conductivity to the first type and a major surface;
• (c) forming a strip of active semiconductor material buried between the major surfaces of the first and second bodies;
• (d) forming a periodic structure in an external surface of the second body extending adjacent to said strip;
• (e) forming at least one mirror-like surface extending transversely from the external surface of the second body at about a 45.degree. angle to said surface and adjacent an edge of the strip to reflect light emitted from the edge of the strip in a plane normal to the major surfaces and out the major surface of the first body;
• and
• (f) forming contact means on said first and second bodies.

A method of forming a heterostructure distributed feedback type laser comprising:

• (a) forming a substrate of semiconductor material having a major surface and a first type conductivity;
• (b) forming a layer of semiconductor material having a conductivity opposite said first type conductivity in the shape of a mesa with an external plateau surface and an underlying surface;
• (c) forming a strip of active semiconductor material of narrower bandgap than the bandgap of the semiconductor material of the substrate or the layer on said major surface of the substrate and embedded between said substrate and said layer;
• (d) forming a periodic structure in the plateau of said layer and extending in parallel proximity with the strip of active semiconductor material;
• (e) forming first ohmic contact means on said plateau adjacent the periodic structure;
• and
• (f) forming second ohmic contact means on said substrate.

The method of forming a laser comprising:

• (a) forming a substrate having a major surface and comprised of semiconductor material having a first type conductivity;
• (b) forming a layer on the substrate in the shape of a mesa having a plateau surface and an underlying surface aligned with the major surface of the substrate, said layer being comprised of semiconductive material of opposite conductivity to said substrate material;
• (c) forming a strip of active semiconductor material between said substrate layer and embedded therein adjacent an undercut portion between the substrate and layer;
• (d) forming a periodic structure for providing a distributed feedback network in the plateau surface of the layer adjacent the strip;
• (e) forming an ohmic contact strip on said plateau surface adjacent said periodic structure and at least partially overlying said undercut portion;
• and
• (f) forming an ohmic contact on said substrate.

The method of forming a laser comprising:

• (a) forming a substrate of semiconductor material having a major surface and a first type conductivity;
• (b) forming a layer of semiconductor material of conductivity opposite said first type conductivity and having a major surface adjacent to the major surface of said substrate and formed in the shape of a mesa with an external plateau surface;
• (c) forming a strip of active semiconductor material embedded between said substrate and layer extending along the major surfaces;
• (d) forming a periodic structure in said plateau surface adjacent said strip;
• said structure comprising corrugations extending into said surface of sufficient depth such that light waves travelling along the region of the active layer interact with proximate portions of the corrugations but not the remote portions;
• (e) forming ohmic contact means on the adjacent remote portions of the corrugations and on said substrate.

The method of forming a laser comprising:

• (a) forming a substrate of semiconductor material having a first type conductivity;
• (b) forming a layer of semiconductor material of opposite type conductivity to the first type;
• (c) embedding a strip of active lasing material between said substrate and layer, said strip having a pair of side walls extending between said substrate and layer with a periodic structure on at least one side wall of said embedded strip;
• and
• (d) forming contact means on said substrate and layer.

Forming a surface emitting laser comprising:

• (a) forming a substrate of semiconductor material having a first type conductivity and a major surface;
• (b) forming a layer of semiconductor material of opposite type conductivity to the first type and a major surface;
• (c) forming a strip of active semiconductor material buried between the major surfaces of the substrate and layer;
• (d) forming a periodic structure in an external surface of the layer extending adjacent to said strip;
• (e) forming at least one mirror-like surface extending transversely from the external surface of the layer at about a 45.degree. angle to said surface and adjacent an edge of the strip to reflect light emitted from the edge of the strip in a plane normal to the major surfaces and out the major surface of the substrate;
• and
• (f) forming contact means on said substrate and layer.

The method of forming a DFB laser heterojunction device from a doped indium phosphide substrate upon which a gallium indium arsenide phosphide active layer is formed and a layer of indium phosphide, doped opposite to said substrate, formed on said active layer, comprising the steps of:

• (a) selectively etching the indium phosphide layer until a mesa of indium phosphide is formed over the active layer and a surface of active layer material is exposed on two sides of said mesa;
• (b) selectively etching only the active layer material at the exposed surfaces until two undercut regions are formed under the mesa with a strip of active material therebetween which is exposed on two sides of said strip;
• and
• (c) filling in the undercut region with indium phosphide from said mesa and substrate sufficient to bury the exposed side portions of said strip;
• (d) forming a grating structure on an exposed surface of either the indium phosphide substrate or the indium phosphide layer.