An internal combustion engine wherein a hydrocarbon feed valve and an exhaust purification catalyst are arranged inside of an engine exhaust passage. The billable events occur from the end-users of the wireless devices selectively communicating with other computer devices across the wireless network and downloading and executing software applications thereupon. Moreover, creation and handling of data can easily be performed. An optoelectronic device includes the structure superposed on a substrate, which can be semiconductive, and the elements of the grating used as electrodes and adapted to allow a potential difference between adjacent elements. The method includes performing an anisotropic-etching process to a P-type epitaxial layer to form a rounded or a right-angled ladder on the sidewall of the P-type epitaxial layer.