The V-I characteristics show the negative resistance region. Carrier velocities are very high. Tunnel Diode : Symbol: It is a highly doped PN Junction diode , used for low voltage high-frequency switching applications. It has a high charge carrier velocity. Microwave frequencies range between 10 9 Hz 1 GHz to GHz Tunnel diodes are not good rectifiers, as they have relatively high leakage current when reverse biased.
Both statements are true and the reason is the correct explanation of the assertion given. Important Points Detailed Explanation: A tunnel diode is a highly doped semiconductor diode. Under Reverse Bias In this case, electrons in the valence band of the p side tunnel directly towards the empty states present in the conduction band of the n side creating a large tunneling current that increases with the application of reverse voltage. Answer Detailed Solution Below Option 2 : a - iv , b - iii , c - i , d - ii.
Tunnel Diode : It works on the principle of tunneling effect, i. It exhibits voltage-controlled negative resistance. It has a very narrow depletion region i. The best material is GaAs having the highest swing. Answer Detailed Solution Below Option 1 : inside valence band of p-type and inside conduction band of n-type semiconductors. Below the Fermi level, all states are filled and above the Fermi level all states are empty.
Analysis : Step 1 : At zero bias there is no current flow as the fermi level are aligned Step 2 : A small forward bias is applied. This will create a forward bias tunnel current Step 3: With a larger voltage, the energy of the majority of electrons in the n-region is equal to that of the empty states holes in the valence band of p-region; this will produce maximum tunneling current Step 4 : As the forward bias continues to increase, the number of electrons in the n side that are directly opposite to the empty states in the valence band in terms of their energy decreases.
Therefore, the decrease in the tunneling current will start Step 5 : As more forward voltage is applied, the tunneling current drops to zero. Under Reverse Bias : In this case the, electrons in the valence band of the p side tunnel directly towards the empty states present in the conduction band of the n side creating large tunneling current which increases with the application of reverse voltage.
Answer Detailed Solution Below Option 1 : i is wrong but ii is correct. Tunnel diode: The tunnel diode is also known as Esaki diode is a type of diode that has a large value of negative resistance. An equivalent circuit diagram of tunnel diode is given by Where, R s is the resistance of the bulk material and contacting plates R j is the negative resistance of the tunnel diode. It is bias-dependent L s is the parasitic series inductance C p is the distributed capacity of the case.
Two frequencies, resistive and reactive cutoff frequency, can be used in defining the practical frequency range of a tunnel diode Resistive cutoff frequency The resistive cutoff frequency, f r0 is that frequency at which the real part of the input impedance, neglecting C p , is zero.
The doping level of the tunnel diode is larger than the normal diode used in rectifier circuits. Due to the high level of doping decreases the area of the depletion region. Due to the thin depletion region, the current can flows through the diode in reverse biased condition and There are no breakdown effects exits for this diode similar to a normal diode shown. Tunnel Diode: A tunnel diode is formed by high doping of p and n regions.
The high doping makes the semiconductors degenerate and conduction is due to the tunneling effect. In the tunnel diode, the dopant concentrations in the p and n layers are increased to a level such that the reverse breakdown voltage becomes zero and the diode conducts in the reverse direction. Applications: Microwave Oscillators High-speed counters Fast rise time pulse generators Practical tunnel diodes operate at a few milliamperes and a few tenths of a volt, making them low-power devices.
Important Points Gunn diode: A Gunn diode is considered as a type of diode even though it does not contain any typical PN diode junction like the other diodes, but it consists of two electrodes. It is also called a Transferred Electronic Device.
It is a negative differential resistance device, which is frequently used as a low-power oscillator to generate microwaves. It consists of only an N-type semiconductor in which electrons are the majority charge carriers. To generate short radio waves such as microwaves, it utilizes the Gunn Effect. The Gunn Effect can be defined as the generation of microwave power power with microwave frequencies of around a few GHz whenever the voltage applied to a semiconductor device exceeds the critical voltage value or threshold voltage value.
It exhibits negative resistance and operates on the principle of avalanche breakdown. Its applications include police radar systems, low power microwave transmitters, etc. Tunnel diodes have a heavily doped PN junction that is about 10 nm wide. The heavy doping results in a broken bandgap, where conduction band electron states on the N-side are more or less aligned with valence band hole states on the P-side.
VI Characteristics of a tunnel diode: When the Tunnel diode is reverse biased, large tunneling current flows. The gallium arsenide, germanium and gallium antimonide are used for manufacturing the tunnel diode. The ratio of the peak value of the forward current to the value of the valley current is maximum in case of germanium and less in silicon. Hence silicon is not used for fabricating the tunnel diode. The doping density of the tunnel diode is times higher than that of the ordinary diode.
Operation and its Characteristics The operation of the tunnel diode mainly includes two biasing methods such as forward and reverse Forward Bias Condition Under the forward bias condition, as voltage increases, then current decreases and thus become increasingly misaligned, known as negative resistance.
An increase in voltage will lead to operate as a normal diode where the conduction of electrons travels across the P-N junction diode. The negative resistance region is the most important operating region for a Tunnel diode. The Tunnel diode and normal P-N junction diode characteristics are different from each other. Reverse Bias Condition Under the reverse condition, the tunnel diode acts as a back diode or backward diode.
With zero offset voltage it can act as a fast rectifier. In reverse bias condition, the empty states on the n-side aligned with the filled states on the p-side. In the reverse direction, the electrons will tunnel through a potential barrier. By using our site, you agree to our collection of information through the use of cookies. To learn more, view our Privacy Policy. To browse Academia.
Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Sohaib Alam. A short summary of this paper. Download Download PDF. Translate PDF. In fact semiconductor technology is present in almost every area of modern day technology and as such semiconductor theory is a very important element of electronics.
A Semiconductor diode is a simple electrical device that allows the flow of current only in one direction. So it can be said to act somewhat like a switch. In its basic form a semiconductor diode is formed by making P-N Junction which is one of the fundamental structures within semiconductor technology.
It is the fundamental building block of semiconductor diodes and transistors and a number of other electronic components.
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