Schottky diode

 Schottky diode 

Schottky diode is an electronics component, which is formed by the junction of a semiconductor with a metal. It has a low forward voltage and very fast switching action. Schottky diode also known as Schottky barrier diode or hot carrier diode or hot electron diode or majority carrier diode.

Which is used in different applications. A scientist named Walter H. Schottky first discovered Schottky diode.

The symbol for the Schottky diode is based around the basic diode circuit symbol.

The symbol of Schottky diode is shown in the figure.  

 symbol

Working: 

Metal of the Schottky diode barrier diode like gold, silver, platinum, molybdenum, tungsten or chromium and N-type semiconductor materials are used. The N-type of semiconductor as a cathode and the metal side act as the anode of the diode.

                                                               

working

A junction is formed by bringing metal contact with a moderately doped N-type semiconductor material. The Schottky diode is unidirectional device conducting current flows only in one direction. Schottky diode is metal to semiconductor junction hence, there is no charge carrier depletion region so it does not have charge storage region therefore it have very fast speed and also Schottky forward voltages is 150- 450 mv this lower forward voltage make better system efficiency. This Schottky barrier results in both very fast switching of the diode and low forward voltage drop. The Schottky diode operates only with majority carriers there is no minority carriers. 

Reverse Recovery time:

The time taken by a diode to switch from the conducting state to non-conducting states is called reverse recovery time. In the Schottky diode as the metal semiconductor junction are used so there is no charge storage region hence, therefore there is no reverse recovery time due to which the switching is very fast. 

When we working on forward biased the higher energy level of electrons in the N-type region are injected into metal region where they give up there excess energy rapidly. Since there are no minority carriers presents therefore it is very rapid response to a change in bias. 

As the frequency increases the action of small signal rectifier diodes begin to spoil, they have no longer ability to switch off fast enough to produce a well defined half wave single so this problem solved by Schottky diode.

Why Schottky barrier diode called as hot carrier diode?

The Schottky barrier diode also called as hot barrier diode because the higher energy level of electrons in the n region as compared to those in metal region. When we working on forward biased the higher energy level of electrons in the N-type region are injected into metal region where they give up there excess energy rapidly. Since there are no minority carriers presents therefore it is very rapid response to a change in bias.     

                                                                  

                                                                                  

V-I characteristics of Schottky barrier diode:

The forward voltage drop of the Schottky barrier diode is very low. The forward voltage drop range from 0.3 to 0.5 volts  and this forward voltage drop of Schottky barrier diode is made up of silicon.  If we increasing the forward voltage drop increases at same time the doping concentration of N-type semiconductor increases gradually. 

                                                             

VI

The V-I characteristics of a Schottky barrier diode very erect as compared to the normal P-N junction diode due to the high concentration of current carriers. 

Some features of Schottky diode:

1: Forward current due to thermionic emission

2: Lower peak reverse voltage 

3: Small operating range 

4: Lower power dissipation

5: Less reverse recovery time 

6: Very fast switching 

7: Used for low power high frequency operations 

                                                        

8: Reverse current only due to majority carriers that overcome the barriers 

9: Cut-in voltage is small 0.3 to 0.5 v

10: Junction capacitance is very low.

Application of Schottky diode: 

1: Schottky diodes is used for clamping and clipping circuits.

2: Rectify high frequencies signal without distortion.

3: Low power TTL logic. 

4: Schottky diode is used in radio frequency .

5: It used in RADAR system.

6: It used as converters (AC to DC).

7: It used to detect the signals. 

8: It used as fast switching device.

Disadvantages :

Schottky diode has higher leakage current/reverse leakage current.