What is the Schottky Diode
- A Schottky Diode is a type diode that has PN junction constituted by the combination of the metal and semiconductor material, and it is the main part of the switching circuitries.
- The main benefit of this diode over the normal semiconductor diode is that during forwarding biasing its voltage loss is very less.
- As this diode uses less power and has less switching time, it not only used as a rectifier, switching circuitries but also used in TTL (transistor-transistor logic) and CMOS (complementary metal-oxide-semiconductor) logic gates circuitries.
- TTL (transistor-transistor logic) Schottky logic gates are distinguished by the notes (LS) that are written on the casing of the module like 74LS00.
- The switching speed of the Schottky diode is more than the traditional diode. The undesired sound during switching is less than the Schottky.
- Due to high speed and less noise, it is mostly used in such circuitries where high speed is required.
- When we applied certain value of the voltage in the forward biased condition the current moves through the Schottky diode due to this current there is some loss of voltage at the diode terminals. This loss is noted as the voltage drop of the diode.
- The voltage deterioration in the general diode is (0.6) volts to (0.7) volts, but in case of the Schottky, it is (0.2) volts to (0.3) volts. This reduction of voltage is the value of the voltage that used to on the diode.
- So we can say that the voltage loss for the Schottky is (0.2) to (0.3) that is less than the normal diode that is (0.6) to (0.7) volts.
What is a Schottky Barrier
- This barrier is similar to the depletion region in the general diode.
- It created at a joining point of the metal and semiconductor material in the Schottky diode.
- We can say that it is a P.E (potential energy) barrier, that created at the joining of the metal and semiconductor material. The electrons in the diodes cross this layer to move another part of the diode.
- There are further 2 types of the Schottky barrier first one is rectifying Schottky barrier and the other one is non-rectifying Schottky barrier.
- In the rectifying barrier, Schottky works like a resistance so it also called ohmic and other is called non-ohmic barrier.
Energy Band of Schottky Diode
- The energy band of the Schottky diode is shown in the given figure, that is built by the n-type material and metal.
- The energy level of the electrons at the outer side of the substance is known as the Vaccum level.
The amount of energy need to move electron from the Fermi level to vacuum level is known as the work function, it is described in the figure.
The value of this energy (work function) is different for metallic and semiconductors. In the case of the metal, its value is higher than the semiconductors substances.
- So the electrons in N-type semiconductor have larger value of P.E than the electrons in metallic.
So the Fermi level of the semiconductors is higher than the metals.
- As electrons in higher energy level have larger P.E then the electrons in lesser energy level.
- Electrons in the n-type substances have larger P.E than the electron in metallic substance.
- Let's see the diagram of the energy band of the Schottky diodes.
V-I characteristics of Schottky diode
- Now we discuss the voltage and current characteristics of the Schottky diode.
- In the given diagram the current is represented on the y-axis of the graph and the voltage is shown on the x-axis of the graph.
- This characteristic curve is similar to the curve of the general diode.
- But the voltage loss in the Schottky diode is less than the general diode.
- As we discussed earlier voltage drop in Schottky is about (0.2) to (0.3) volts but in general diode, its value is (0.6) to (0.7) volts.
Difference Between Schottky Diode and General Diode
- There are some differences among the Schottky and general diodes that are described here.
- As in the Schottky, there is metal so due to this metal, there are a lot of electrons than the holes so mostly current flows due to these electrons. Due to this feature schottky diode is also known as the uni-polar component.
- But in case of the normal diode the current flows due to the holes and electrons, it also is known as the bipolar component.
- The reverse breakdown in the Schottky diodes occurs at the lesser voltage while in general diode it occurs at higher voltages.
- As there is a depletion layer exists in the general diodes but in Schottky diode, this layer does not form.
- The operating voltage of the Schottky diode is less than the normal diode, operating voltage for Schottky is 0.2 to 0.3 volts while in case of the general diode is 0.6 to 0.7 volts.
- In the Schottky diode, the electrons are in excess in both metal and semiconductor portion, but in general diodes, electrons are in excess in the N- portion and holes are in access in the P-portion.
Advantages of Schottky diode
- These are some benefits of the Schottky diode that are described here.
- As we all are familiar with the capacitance, it is the capacity of the capacitor to store charges.
- In the case of the general diode, there is a depletion layer that has positive and negative charges that form a capacitor like an assembly.
- But in the Schottky diodes, there is no depletion region so capacitance junction does not exist in the Schottky.
- As there is no depletion region in the Schottky diode, so smaller value of current applied will produce a larger current in the diode.
- The operating voltages for the Schottky diode are very less as compare to the general diode, its value for Shottky is 0.2 to 0.3 volts, for the PN junction diode is 0.6 to 0.7 volts.