A diode rectifier formed by making a point contact between a small metal wire with a sharp point and a semiconductor. The point-contact diode has a very small area, which results in a very small capacitance, and it is therefore suitable for microwave applications. It has however a large spreading resistance, a large leakage current, and poor reverse breakdown characteristics. Its characteristics are difficult to predict since the device is subject to wide variations in its physical properties, including the pressure of the wire whisker, the contact area, and the crystal structure.