Mounting technology for intersubband light emitters

A method of fabricating an intersubband semiconductor laser comprising the steps of:

• (a) providing a single crystal semiconductor substrate,
• (b) forming on said substrate an epitaxial region that includes a core region and an intersubband active region in said core region, said forming step (b) including the steps of (b1) forming upper and lower cladding regions bounding said core region, (b2) forming at least said upper cladding region and said active region in the shape of an elongated mesa having sidewalls and a top surface, (b3) forming a patterned first insulating layer over said mesa, said first layer having an opening that exposes said top surface, and wherein said electrode forming step (d) includes the step of (d1) forming said electrode on said first layer and on said top surface,
• (c) forming front and back facets on opposite ends of said mesa so as to define an optical cavity resonator, said active region being disposed in said resonator,
• (d) forming a metal electrode on said sidewalls and top surface of said mesa so as to provide an electrical connection to said active region, and
• (e) mounting said laser on a surface of a heat sink, characterized in that
• said mounting step (e) includes the steps of (e1) soldering said electrode to said heat sink with In-based solder so that said front facet overhangs an edge of said heat sink and (e2) cleaving off the overhanging portion of said laser so as to form a new front facet that is essentially flush with said edge of said heat sink,
• said mounting step (e) includes designing said heat sink so that said surface is electrically conducting all the way to said edge and said soldering step (e1) causes said solder to adhere to said surface and to extend all the way to said edge,
• said forming step (b3) includes the step of forming said insulating layer from a material that is not wet by said In solder,
• said electrode forming step (d) includes the step of recessing said electrode from the edges of said laser by a distance of at least 10 μm, and
• said facet forming step (c) includes the steps forming an insulating second layer on said back facet and forming a metal layer on said second layer so that any solder that would tend to flow onto said back facet contacts said metal layer and not the semiconductor material of the back facet.