Baritt diode, Construction, working and V-I characteristics

What is Baritt diode?

Baritt diode is the acronym of Barrier Injection Transit Time diode. This diode is used in microwave signal generation. It works based on thermionic emission (electrons are discharged when temperature is increased). whereas other diodes works on avalanche multiplication. So it is less noisy.  

Microwave oscillations takes place in the Baritt diode takes place due to thermionic emission and diffusion of minority carrier across the forward biased barrier.

Construction of Baritt diode:

Construction of Baritt diode

 

Baritt diode is a two terminal three layer device .It has a M-N-M structure. Basically Baritt diode consists of two back to back diodes it can be P type and N type or Metal and semiconductor or combination of two.

Working  of Baritt diode:

Working of Baritt diode

 

The N type region is larger than the both P type. So punch through effect occurs between these regions. “Punch through effect” is the effect which happens when the depletion region expands from one junction to the other junction. 

When Emitter is connected to the positive terminal and collector is connected to the negative terminal, it is said to be forward bias. 

In the forward bias emitter base will be in the forward mode and the collector base will be in the reverse bias mode. Operation is limited around 25 GHz for silicon and 90 GHz for GaAs

V-I Characteristics of Baritt diode:

V-I characteristics of Baritt diode

In the V-I characteristics of Baritt diode, we can see the Vpt which is the punch through voltages. It differs for both the directions and it can be controlled during the manufacturing and construction process. 

Voltage and current waveforms:

Voltage and current waveform

When the voltage is applied to the device, the potential drop happens in the reverse bias. When the voltage is increased further till the end of the depletion region, the punch through happens.

The depletion region is free of charges and the punch through of the charge carriers happens here. After the charge carriers are injected, it travels to the base with the saturation velocity.

After the charge carriers are injected, due to the positive resistance region of Baritt diode it results in non ideal current waveform. The width of the terminal current depends on the ON time or the transit time.

 

Advantages

 

• It works on thermionic emission so it produces very low noise.

 

Disadvantages

 

• When the frequency is increased, the efficiency decreases.
• It produces low power output.
• Bandwidth is very narrow.

Application of Baritt diode:

• It is used in Burglar alarms
• It is used as Oscillator
• It is used as small signal amplifier