Light-emitting diode: It has unidirectional conductivity. Only when the applied forward voltage makes the forward current large enough, the light will be emitted. The larger the forward current, the stronger the light will be.
Point contact diodes have small currents and junction capacitances, and are suitable for high-frequency circuits and switching circuits.
Surface contact diodes have large junction area, large current and large junction capacitance, and are suitable for low-frequency rectifier circuits.
Planar diodes can pass larger currents when the junction area is large, and are suitable for high-power rectification. When the junction area is small, they can be used as switching tubes in digital circuits.
