Semiconductor

Question 1

Intrinsic Semiconductor (Pure)

Answer 1

A semiconductor with no impurities added. Examples: Silicon (Si) and Germanium (Ge)

Question 2

Carrier Concentration (Intrinsic)

Answer 2

In an intrinsic semiconductor electron concentration equals hole concentration: ne = nh = ni.

Question 3

Carrier Mobility (Intrinsic)

Answer 3

Electron mobility is greater than hole mobility: μe > μh.

Question 4

Majority Carriers (Intrinsic)

Answer 4

None. Electrons and holes are present in equal numbers.

Question 5

Mass Action Law

Answer 5

The product of electron and hole concentrations is constant: ni^2 = ne × nh.

Question 6

Effect of Temperature on Intrinsic Semiconductor

Answer 6

As temperature increases the number of electrons and holes increases.

Question 7

Extrinsic Semiconductor

Answer 7

A pure semiconductor doped with impurities to modify its electrical conductivity.

Question 8

N-Type Semiconductor Dopant

Answer 8

Pentavalent impurity with five valence electrons.

Question 9

Majority Carriers (N-Type)

Answer 9

Electrons.

Question 10

Carrier Concentration (N-Type)

Answer 10

Electron concentration is much greater than hole concentration: ne ≫ nh.

Question 11

Donor Energy Level

Answer 11

In N-type semiconductor donor level lies just below the conduction band.

Question 12

Net Charge of N-Type Semiconductor

Answer 12

Zero. The semiconductor remains electrically neutral.

Question 13

P-Type Semiconductor Dopant

Answer 13

Trivalent impurity with three valence electrons.

Question 14

Majority Carriers (P-Type)

Answer 14

Holes.

Question 15

Carrier Concentration (P-Type)

Answer 15

Hole concentration is much greater than electron concentration: nh ≫ ne.

Question 16

Acceptor Energy Level

Answer 16

In P-type semiconductor acceptor level lies just above the valence band.

Question 17

Net Charge of P-Type Semiconductor

Answer 17

Zero. The semiconductor remains electrically neutral.

Question 18

Diffusion Current in P-N Junction

Answer 18

Due to movement of majority carriers (Holes: P → N

Question 19

Drift Current in P-N Junction

Answer 19

Due to movement of minority carriers (Holes: N → P

Question 20

Forward Biased P-N Junction

Answer 20

Positive terminal connected to P-side and negative terminal to N-side.

Question 21

Current in Forward Bias

Answer 21

Current is mainly due to majority charge carriers.

Question 22

Depletion Width in Forward Bias

Answer 22

Depletion region width decreases significantly.

Question 23

Resistance in Forward Bias

Answer 23

Very small resistance.

Question 24

Reverse Biased P-N Junction

Answer 24

Positive terminal connected to N-side and negative terminal to P-side.

Question 25

Current in Reverse Bias

Answer 25

Very small current due to minority charge carriers.

Question 26

Depletion Width in Reverse Bias

Answer 26

Depletion region width increases significantly.

Question 27

Resistance in Reverse Bias

Answer 27

Very large

Question 28

Knee Voltage (Barrier Potential)

Answer 28

Minimum forward voltage at which diode current rises rapidly (≈0.7 V for Si

Question 29

Breakdown Voltage

Answer 29

Reverse voltage at which diode current increases sharply.

Question 30

Zener Diode Application

Answer 30

Used as a voltage regulator.

Question 31

Zener Diode Operation

Answer 31

Maintains constant voltage when reverse biased in breakdown region (Vapplied > Vzener).

Question 32

Zener Diode Doping

Answer 32

Heavily doped leading to a thin depletion region.

Question 33

LED (Light Emitting Diode)

Answer 33

A forward-biased highly doped P-N junction that emits light (e.g.

Question 34

Photodiode

Answer 34

A reverse-biased lightly doped P-N junction used to detect light.

Question 35

Photodiode Current

Answer 35

Reverse photocurrent is proportional to the intensity of incident light.

Question 36

Solar Cell

Answer 36

Operates on photovoltaic effect without external bias.

Question 37

Voc (Solar Cell)

Answer 37

Open circuit voltage: maximum voltage when output current is zero.

Question 38

Isc (Solar Cell)

Answer 38

Short circuit current: maximum current when output voltage is zero.

Question 39

Slope of V-I Graph

Answer 39

Represents conductance (1/R) and equals ΔI/ΔV.

Question 40

Dynamic Resistance of Diode

Answer 40

Resistance at a given operating point: Rdynamic = ΔV/ΔI (reciprocal of slope).

Question 41

Two main types of batteries

Answer 41

Primary (non-chargeable) and Secondary (chargeable)

Question 42

Primary batteries (definition)

Answer 42

Reaction occurs only once; cannot be reused or recharged

Question 43

Leclanché cell (common name)

Answer 43

Dry cell

Question 44

Leclanché cell anode

Answer 44

Zinc container