This specification discloses pcLEDs in which the wavelength converting structure comprises one or more layers of phosphor particles disposed on a transparent substrate at high packing density. The particles are coated with an inorganic non-absorbing layer which mechanically stabilizes the phosphor particle layers and provides a thermally conductive connection between the phosphor particles. The wavelength converting structure is attached to a semiconductor LED die with the transparent substrate of the wavelength converting structure facing away from the die by a thin glue layer that bonds a light emitting surface of the die to the phosphor particle layers. Methods for fabricating such pcLEDs are also disclosed.