Semi-Conductor Questions

Question 1

How do you estimate the concentration of electrons and holes in a p-type semiconductor?

Answer 1

n_p refers to the concentration of electrons

Question 2

How do you calculate the concentration of electrons and holes in an n-type semiconductor?

Answer 2

p_n refers to hole concentration

Question 3

What Hall voltage do you expect for a positive majority carrier ?

And negative majority carrier?

Answer 3

Positive

Negative

Question 4

What is the Hall coefficient ?

Answer 4

Question 5

What equation would you use to calculate the built-in voltage of a silicon PN junction?

Answer 5

Question 6

The equation that relates the depletion region width (lengths) to the concentration?

What does it tell us?

Answer 6

Tells us that depletion regions can only be symmetric if the donor and acceptor concentration are equal.

x_n region of the donor , n for negative

x_p region of the accepto, p for positive

Question 7

What does a reverse bias in a pn junction do to the built-in voltage?

Answer 7

It increases the built in voltage and increases the barrier potential.

Question 8

Graphical representation of the effect a reverse and forward bias has on the diffusion current.

Answer 8

Question 9

The equation for I_total through a pn junction ?

What is this equation essentially?

Answer 9

The equation for current through a diode.

Question 10

What do you call the terminal of a diode where the current flows into?

Answer 10

anode(+)

Question 11

What do you call the terminal of a diode where current flows out of ?

Answer 11

cathode (-)

remember current flows from positive to negative.

Question 12

What is the equation for current density?

Answer 12

Question 13

What does a direct bandgap semiconductor emit?

Answer 13

Through radiative recombination it releases photons.

Question 14

The equation for the energy of a photon?

Answer 14

Question 15

If you have the band gap energy, what equation do you use to determine the wavelength?

Answer 15

Question 16

The equation for current through solar cell ?

Answer 16

Question 17

Sketch the IV characteristic of a solar cell in the dark and under light.

Include all details.

Where is the region of interest for extracting solar power?

Answer 17

Include I_photo and V _oc

and the region for extracting power

Question 18

What is the equation for the short circuit current for a solar cell ?

Answer 18

Question 19

What does it mean that the IV(power) characteristic for a solar cell is in the negative quadrant?

Answer 19

If it’s negative it means that power is being extracted from the device.

Question 20

The easy way of determining maximum power rectangle of a solar cell?

Answer 20

take the product of I_sc and V _oc

Then multiply by 0.8.

Question 21

The equation for the oxide capacitance of a MOSFET?

Answer 21

Where epsilon is the numerator

and

t_ox thickness of oxide layer

Question 22

The equation for overdrive voltage?

Answer 22

Question 23

State which of the materials given in Table 7.1 would be suitable for use in an LED, and why.

Answer 23

LEDs work when the PN junction is in the forward bias.

LEDs are based on electron-hole recombination.

The electromagnetic energy they release is equal to the band gap energy.

Question 24

For each number, name the region and suggest a specific material (including dopants) from which it can be made.

Answer 24

Question 25

The equation to calculate the concentration of electrons in the conduction band.

Answer 25

Question 26

What is the unit for electron or hole concentration?

Answer 26

cm^-3