SILICON, gallium arsenide, and germanium) RATHER than through vacuum tubes.A CONVENTIONAL solid-state diode will not let significant current flow if REVERSE-biased below its reverse breakdown voltage. Hence Zener diode is a solid-state device.Zener diode:A Zener diode is USED as a voltage regulator.The slope (V / I) is positive.The forward voltage rating of the Zener diode is the same as a normal diode.At reverse breakdown voltage (typically around 5V), there is a sharp breakdown at a reverse voltage as shown in the figure: