GaInAsP/InP Double-heterostructure lasers

The method of forming a semiconductor device comprising the steps of:

• (a) making a body by:
• (i) forming a substrate;
• (ii) forming a first layer of semiconductor material on the substrate;
• (iii) forming a second layer of semiconductor material on the first layer;
• and
• (iv) selectively forming coatings over portions of the second layer;
• (b) selectively removing portions of said second layer down to the top surface of the first layer forming at least a first mesa, and a control mesa on said first layer;
• (c) etching said first layer underlying the mesas to produce an undercut area beneath the mesas until the first layer material underlying the control mesa is removed;
• and
• (d) heating the body to cause the remaining material in the region of the undercut area to migrate into the undercut area adjacent the first mesa.

The method of forming a semiconductor laser comprising the steps of:

• (a) making a unitary structure by:
• (i) forming a substrate of material doped to a predetermined level of conductivity;
• (ii) forming an active layer of semiconductor material over said substrate;
• (iii) forming a top layer of semiconductor material doped to a predetermined second level of conductivity;
• (iv) forming a protective coating over a portion of said top layer;
• (b) removing a portion of said top layer on two adjacent sides of said protective coating down to the top surface of said active layer;
• (c) removing a portion of said active layer underlying adjacent sides of said top layer so as to produce undercut areas beneath the remaining top layer with a volume of active layer therebetween;
• the sides of said volume being exposed at the undercut areas and
• (d) heating the unitary structure in a controlled environment to a temperature which causes the material in the regions of the undercut areas to migrate into the undercut area.

The method of forming a mirror surface on a semiconductor device comprising the steps of:

• (a) making a body by:
• (i) forming a substrate;
• (ii) forming an active layer of semiconductor material on the substrate;
• (iii) forming a top layer on the active layer;
• and
• (iv) forming a coating over a portion of the top surface substantially perpendicular to an adjacent side of the sample;
• (b) removing a portion of said top layer on said adjacent side down to the top surface of the active layer;
• (c) removing a portion of said active layer underlying the remaining top layer to produce an undercut area beneath the remaining top layer;
• (d) heating the body to cause the material in the region of the undercut area to migrate into the undercut area adjacent the active layer;
• and
• (e) removing further material on the top layer and substrate including the migrated material until a smooth mirror surface is formed on said adjacent side of the sample.

The method of forming a mirror surface on a heterostructure semiconductor laser device comprising the steps of:

• (a) making a heterostructure by:
• (i) forming a substrate;
• (ii) forming an active layer of quaternary III-V alloy semiconductor material on the substrate;
• (iii) forming a top layer of a binary compound semiconductor material on the active layer;
• and
• (iv) forming a coating over a portion of the top surface of the top layer substantially perpendicular to an adjacent side of the sample;
• (b) removing a portion of said top layer on said adjacent side down to the top surface of the active layer by etching said binary compound but not said III-V alloy;
• (c) removing a portion of said active layer underlying the remaining top layer to produce an undercut area beneath the remaining top layer by etching said quaternary III-V alloy but not said binary compound;
• and
• (d) heating the heterostructure to cause the material in the region of the undercut area to migrate into the undercut area adjacent the active layer.

The method of forming a buried layer of quaternary III-V material in a heterojunction device having alternate layers of quaternary III-V material and binary III-V material comprising the steps of:

• (a) selectively etching only the binary material until a mesa of binary material is formed over the layer of quaternary material and a surface of quaternary material is exposed on two sides of said mesa;
• (b) selectively etching only the quaternary material at the exposed surfaces until two undercut regions are formed under the mesa with a layer of quaternary material therebetween which is exposed on two sides;
• and
• (c) filling in the undercut region with binary material from said mesa sufficient to bury the exposed portions of said quaternary material.