PN Junction diode:
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| Symbol of PN Junction diode |
PN Junction Diode is the most commonly used semiconductor device. As the name says PN Junction Diode is the interface of P type semiconductor material and N type semiconductor material. P type is doped with trivalent impurity and the majority carrier is holes and N type is doped with pentavalent impurity and the majority carrier is electrons. Very useful property of PN Junction diode is it allows electrons to flow in only one direction and thus current flows in only one direction , in the other direction it does not allow current to flow. It is made up of semiconductor materials like Silicon, Germanium and Gallium Arsenide.
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Zener Diode:
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| Symbol of Zener diode |
Zener diode is specially designed, heavily doped diode which operates in both forward and reverse biased condition when enough voltage is applied, unlike the PN Junction diode which does not conduct when it is reverse biased. Normally in PN junction diode the breakdown voltage is so high , so when it is reverse biased it damages the diode permanently. But zener diode is designed in such a way that breakdown voltage is less. Zener Diode is also called as breakdown Diode. Diodes are manufactured with different zener voltages. It is used as a voltage regulator.
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Light Emitting Diode:
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| Light Emitting diodes |
Light emitting diode or LED is similar to the semiconductor PN Junction diode. When it is forward biased the holes from P type and electrons from N type combine with each other and it emits energy in the form of light and when reverse biased the current does not flow. The colour of the LED depends on the nature of the semiconductor material used in the manufacturing of the diode. Available LED colours are red, green , blue , yellow , amber and white.
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Photo diode:
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| Symbol of photo diode |
Photo diode is a semiconductor device which converts light energy into electric current. When it is exposed to light , it absorbs the light and forms the electron hole pairs, thus generates the current.
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Schottky Diode:
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| Schottky diode |
Schottky Diode is constructed by joining N type semiconductor material and a metal electrode together. The junction of semiconductor and the metal is called Schottky barrier. This diode is named after the German Physicist Walter H. Schottky. This diode has a low forward voltage drop and switches over very fastly.
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Shockley diode:
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| Shockley diode |
Shockley diode or PNPN junction is a four layer diode, it has more than one PN junction. This diode is named after its inventor William Shockley. This diode is not commercially available, but it was more useful in making other types of thyristors like DIAC, TRIAC and SCR.
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Laser Diode:
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| Symbol of Laser diode |
Laser Diode is a PN Junction semiconductor diode which converts electric energy into light when external voltage is applied. LASER is the abbreviation of Light Amplification by Stimulated Emission of Radiation.
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Varactor diode:
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| Symbol of Varactor diode |
Varactor diode is named because of its variable capacitance property of the diode. The capacitance is varied by changing the width of the depletion region by controlling the reverse biased voltage. It always works reverse biased condition. The other names of varactor diode are varicap, voltcap, variable capacitance or tunning diode.
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Tunnel diode:
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| Symbol of Tunnel diode |
Tunnel diode is a heavily doped PN Junction diode which shows negative resistance. It works on the basis of tunneling effect. It means the electrons passes through the wall or the barrier and reappearing at the other side. It is also called Esaki diode, named after the inventor Leo Esaki who invented in August 1957 and received Nobel prize in 1973 in Physics for discovering electron tunneling effect used in this diodes.
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GUNN Diode:
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| Symbol of GUNN diode |
GUNN diode is a semiconductor diode made up of N type semiconductor material only. It does not have PN Junction like the other diodes. So it has only electrons as the majority charge carriers and it has two electrodes. Mainly used as low power oscillator to generate microwave.
To know more gunn diode construction and working
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