Electronic Devices and Circuits

Diffusion

Question 1
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Pass Ratio : 50%
What does dn/dx represent?
Velocity gradient
Volume gradient
Density gradient
None
Explanation:
dn/dx represent velocity gradient.
Question 2
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Calculate the diffusion constant for the holes when the mobility of the holes is 400cm2/V-s and temperature is 300K?
1.035m m2/s
0.035m m2/s
1.5m m2/s
1.9m m2/s
Explanation:
Dp=VT*μn
Question 3
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Calculate the diffusion constant for the electrons when the mobility of the electrons is 325cm2/V-s and temperature is 300K?
0.85 m2/s
0.084 m2/s
0.58 m2/s
0.95 m2/s
Explanation:
Dn=VT*μn
Question 4
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What is the SI unit of electron diffusion constant?
cm2/s
m2/s
m/s
none
Explanation:
J=eDdn/dx
Question 5
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Which of the following parameter describes the best movement of the electrons inside a semiconductor?
Velocity gradient
Diffusion
Mobility
Density gradient
Explanation:
Mobility is defined as the movement of the electrons inside a semiconductor. On the other hand, velocity gradient is the ratio of velocity to distance.
Question 6
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Which is the correct formula for the Jp?
Jp=qDdp/dx
Jp=pDdn/dx
Jp=-qDdp/dx
None
Explanation:
Jp is negative for the p type of semiconductors.
Question 7
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Which of the following term isn’t a part of the total current density in a semiconductor?
Temperature
µ
e
E
Explanation:
J=enµE+epµE+eDdn/dx-eDdp/dx
Question 8
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Calculate the diffusion current density when the concentration of electron varies from the 1*1018 to 7*1017 cm-3 over a distance of 0.10 cm.D=225cm2/s
100 A/cm2
108 A/cm2
0.01A/cm2
None
Explanation:
J=eDdn/dx
Question 9
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What is the direction of the electron diffusion current density relative to the electron flux?
Same direction
Opposite to each other
Perpendicular to each other
At 270 degrees to each other
Explanation:
From the graph between electron concentration and the distance, we can see that the direction of the electron diffusion current density is opposite to the electron flux.
Question 10
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In diffusion, the particles flow from a region of _______ to region of ___________
High, low
Low , high
High , medium
Low, medium
Explanation:
Diffusion is the process of flow of particles form the region of the high concentration to a region of low concentration.