The static current voltage characteristics of a tunnel diode consist of (a) Tunneling current and thermal current (b) Thermal current and excess current (c) Tunneling current only (d) Tunneling current, excess current and thermal current Out of these which are correct ?
(d) is correct but (a) is wrong
The three currents that make up a tunnel diode characteristic. Walking along the forward I–V curve from zero bias, each region is dominated by a different mechanism:
1. Tunnelling (band-to-band) current. Because both sides are degenerately doped, the junction is only about 10 nm wide and filled states on the n-side face empty states at the same energy on the p-side. Electrons tunnel straight through the barrier, giving a current that rises to the peak IP and then falls as the bands slide out of alignment — the negative-resistance region.
2. Excess current. At the valley the tunnelling current should fall to zero, but a measurable current remains. It flows by tunnelling via defect and impurity states inside the forbidden gap, and it is what sets the valley current IV and hence the peak-to-valley ratio.
3. Thermal (normal diode injection) current. Beyond the valley the bands no longer overlap, ordinary minority-carrier injection takes over, and the curve climbs like a conventional diode following \(I=I_S\left(e^{qV/\eta kT}-1\right)\).
So the complete static characteristic contains all three, which is statement (d). Statement (a) is incomplete (it omits the excess current) and (c) is plainly wrong, so the option that says "(d) is correct but (a) is wrong" is the answer.
Reading the option list. Note the unusual phrasing: three of the four options are claims about the statements rather than lists of them. Option 4 ("(b) and (d) are wrong") fails because (d) is right; option 2 fails because (c) is wrong and (d) is right — the exact reverse of what it asserts.
Why the shape matters. The negative-resistance stretch between peak and valley lets the tunnel diode act as an amplifier or oscillator at microwave frequencies, and since tunnelling is not transit-time limited it works into the gigahertz range. The figure of merit is the peak-to-valley current ratio, which is precisely why the excess current — the smallest of the three components — is worth naming separately.
Hence, the correct choice is (d) is correct but (a) is wrong.
Similar Questions
A PIN diode can not be used as
i. Microwave switch
ii. Microwave mixer
iii. Microwave detectorWhich is correct ?
________ diode is not used as a microwave mixer or detector.
Match the given lists :
List – I (Name of the Device) List – II (Application) a. Diode i. Rectification b. Tunnel diode ii. Microwave switching c. Zener diode iii. An oscillator d. PIN diode iv. Voltage regulation Codes :
An important figure of merit for microwave application of Schottky diode is forward bias cut off frequency fco and is given by :
Assertion (A) : A tunnel diode consists of simple p-n junction mode of degenerate semiconductor. The current voltage characteristics consists of three components and shows the negative differential region over part of the forward characteristics.
Reason (R) : In tunnel diode the p-side is highly doped and n-side is highly doped and also used as detector.
Varacter diodes have the following properties :
A. Junction capacitance varies with bias voltage
B. Junction capacitance varies with time
C. Non linearity of varacter diodes makes them suitable for frequency multipliers
D. Linearity of varactor diode makes them suitable for frequency multipliers.
Choose the correct answer from the options given below:
In a tunnel diode, the degeneracy on the n-side can be expressed as
Match the following :
List – I List – II a. Gunn diode i. degenerate silicon b. Tunnel diode ii. n-type Ga As c. BJT iii. Silicon d. Diode (P-N junction) iv. \(I_o\left[\exp\left(\dfrac{qV}{kT}\right)-1\right]\) Choose the correct answer from the codes given below:
A TRAPATT diode has the doping concentration NA = 2 x 1015/cm3 and a current density of 20 kA/cm2. The value of avalanche zone velocity is given by :
Assertion (A) : The Gunn diode characteristics shows the region of negative resistance.
Reason (R) : The Gunn diode is made of n-type and p-type degenerate semiconductor.
Select your answer using the codes given below.
Important Questions from Types of Diode
For which of the following diodes when the voltage is increased the current flowing through it decreases?
Which of the following is the main application of Zener diode?
A tunnel diode is
When we tune in any desired station in a radio receiver by rotating the tuning control we vary
Which diode is used as a voltage regulator?
