A novel submount for the efficient dissipation of heat away from a semiconductor light emitting device is described, which also maintains efficient electrical conductivity to the n and p contacts of the device by separating the thermal and electrical conductivity paths. The submount comprises at least the following constituent layers: a substrate (400) with thermally conductive properties; a deposited layer (402) having electrically insulating and thermally conducting properties disposed on at least a region of the substrate having a thickness of between 50 nm and 50 microns; a patterned electrically conductive circuit layer (404) disposed on at least a region of the deposited layer; and, a passivation layer at least partially overcoating a top surface of the submount. Also described is a light emitting module employing the substrate and a method of manufacture of the submount.