A method for forming a light emitting diode includes: (a) growing epitaxially an epitaxial film over an epitaxial substrate; (b) roughening an upper surface of the epitaxial film; (c) forming a top electrode on the roughened upper surface of the epitaxial film; (d) detachably attaching a temporary substrate over the roughened upper surface of the epitaxial film; (e) roughening the lower surface of the epitaxial film; (f) disposing the roughened lower surface of the epitaxial film on a reflective top surface of an electrically conductive permanent substrate; (g) filling an optical adhesive in a gap between the roughened lower surface of the epitaxial film and the reflective top surface of the permanent substrate; and (h) after the step (g), removing the temporary substrate from the epitaxial film.