Disclosed herein is a technique for forming a high quality ohmic contact utilizable in the fabrication of short-wavelength light emitting diodes emitting blue and green visible light and ultraviolet light, and laser diodes using a gallium nitride semiconductor. In a door body 30, an outer surface 31a of a plate part 31 is formed by a composite material layer 60, and a side of an inner surface 31b and a flange part 32 are formed by a metallic material layer 61. Data transfer between the program sections is synchronized by providing a buffer.