The identity of a mobile communication device can be authenticated to allow the device to access a web site without the need for a user log-in operation. In accordance with the invention, the device comprises at least one passive oscillating circuit with an inductor and a capacitor. The slider includes a spring that drives the slider in a direction of card ejection. In a case that the substrate is a p-type, the buffer layer may be an n-type material layer and the current blocking layer may be a p-type material layer.