Electronic device submounts including substrates with thermally conductive vias

A submount for an electronic device, the submount comprising:

• a substrate including first and second major surfaces on opposite sides of the substrate;
• a surface insulating layer on the first major surface of the semiconductor substrate;
• an electrically conductive die attach pad on the surface insulating layer, wherein the electrically conductive die attach pad is electrically insulated from the substrate by the surface insulating layer;
• a heatsink contact pad on the second major surface of the substrate;
• and
• a thermal conduction member extending from the second major surface of the substrate through the substrate toward the first major surface of the substrate, wherein the thermal conduction member is between the electrically conductive die attach pad and the heatsink contact pad and is electrically insulated from the electrically conductive die attach pad, and wherein the thermal conduction member has a higher thermal conductivity than a thermal conductivity of the substrate.