US Patent 7659553 Light-emitting semiconductor device protected against reflector metal migration

An LED has a light-generating semiconductor region formed on a baseplate via a metal-made reflector layer. The light-generating semiconductor region has an active layer sandwiched between a pair of claddings of opposite conductivity types. An annular marginal space is left around the reflector layer between the light-generating semiconductor region and the substrate. In order to preclude the thermal migration of the reflector metal onto the side surfaces of the light-generating semiconductor region, with a possible short-circuiting of the pair of claddings across the active layer, an anti-migration seal is received in the annular marginal space created around the reflector layer between the light-generating semiconductor region and the baseplate.