Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Electrical Engineering > Semiconductors > Flashcards

Semiconductors Flashcards

1
Q

Whats the conductivity of Silicon?

A

10^-2 to 10^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the relationship between radius and energy level in atoms?

A

Energy increases with radius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How can energy for orbit change be supplied to electron?

A

Light or Heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is energy state spit?

A

Something that happens when adjacent atoms interact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the gaps between energy bands called?

A

Band Gaps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is an energy band?

A

A range of allowed energy levels in a Solid formed by the overlap of orbitals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where are all the electrons at T = 0K and what band is empty

A

Valence Band, Conduction band is empty

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many valence electrons does Silicon have

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens to the electrons of Silicon at 0K?

A

They are bound to the Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Is Silicon conductive at 0K

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How much energy is required to lift an electron into the conduction band for Silicon?

A

1.1 eV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What density of free electrons called?

A

Intrinsic Conduction Carrier Density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the relation between temperature and free electron number?

A

Number of free electrons increases with temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is generation?

A

when an electron leaves the band leaving behind a hole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is recombination?

A

When an free electron returns to fill the hole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the thermodynamic equilibrium of generation and recombination?

A

Free electron formation and electrons returning to valence band

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the conductivity of a material depend on?

A

Number of electrons in conduction band which depends on the smaller band gap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is an n-doped semiconductor?

A

A semiconductor in which some silicon atoms have been replaced with a pentavalent element like phosphorus so that the fifth electron has a small band gap which leads to more free electrons than holes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are majority and minority charge carriers in n-doped semiconductors?

A

Electrons are majority charge carriers, holes are minority charge carriers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a p-doped semiconductor?

A

Semiconductor in which some silicon atoms are replaced with trivalent element like boron so the band gap to the valence band is very small and electrons can be easily absorbed leading to more holes than free electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are majority and minority charge carriers in p-doped elements?

A

Holes are majority charge carriers and electrons are minority charge carriers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When can current flow in a semi-conductor?

A

When electrons or holes can move freely

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the formula for current density s?

A

s = I/A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the total current density?

A

Sum of electron and hole current density?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the two physical causes of a current?

A

Drift and diffusion current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How do holes and electrons respond to an electric field with semiconductor?

A

Holes move with the Electric Field and Electrons move against it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What causes Drift current?

A

Application of electric field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is a property of velocity of carriers in drift current?

A

Velocity is constant because of lack of arbitrary accelerations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the formula for charge carrier velocity?

A

v_n = -\micro_n E
v_p = \micro_p E

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How does carrier mobility vary with electric field strength and temperature and doping density?

A

Is constant with lower electric field strength and decreases with increasing field strength due to scattering. Similarly,
it decreases with increasing temperature and doping density.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the formula for current density of charge carriers?

A

s_drift,n = q* n * \micro_n * E

s_drift,p = q* p * \micro_p * E

where n is the electron density, p is the hole density and q is the elementary charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the formula for total drift current?

A

s_DRIFT = \sigma E

where sigma is the electrical conductivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Does diffusion current depend on electric field or charge of particle?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is diffusion current?

A

Movement of particles from region of higher to lower concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What are the formulas for diffusion currents?

A

s_diff,n = qD_n dn/dx

s_diff,p = qD_p dp/dx

Where the D values are the diffusion coefficients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What happens when you join a p and n doped region?

A

Diffusion motion where electrons move to the p-doped region and holes to the n-doped region

Formation of depletion region

Creation of electric field that counteracts diffusion current with drift current

Thermodynamic Equilibrium of diffusion and drift current

37
Q

What is the basic use of a p-n junction>

A

Blocking or conduction of a current by applying different voltages (semiconductor diode)

38
Q

What is the flow direction and blocking direction in p-n juction?

A

n-side is flow and p-side is blocking

39
Q

What happens if you apply voltage in the flow direction of p-n junction?

A

Diffusion dominates,

depletion region decreases,

Electrons flow from n-region to p-region,

Electric field of p-n junction is decreased

Current > 0

40
Q

What happens if you apply voltage in blocking direction of p-n junction?

A
  • Electric field of junction is enhanced
  • Drift motion dominates
  • Current < 0 but very small
  • Electron-hole pairs generated
  • Depletion region increases
41
Q

What is the Diode Equation?

A

I_D = I_S *( exp( U_pn/U_T ) -1)

Where I_D is the diode current, I_S is the saturation current and U_T is the temperature voltage

42
Q

What happens if the voltage increases too much in blocking direction of diode?

A

There is a breakthrough and current increases sharply

43
Q

What are the three types of breakdowns in a p-n junction?

A

Avalanche

Tunnel/Zener

Thermal

44
Q

What are Z-diodes?

A
  • Diodes that use tunnel breakthrough
45
Q

What are the applications of Z-diodes?

A
  • Voltage limitation
  • Voltage stabilization
  • Design for operation in reverse direction
46
Q

How do LEDs work?

A
  • Electrons cross the pn-junction and recombine with holes when a
    positive voltage is applied in the forward direction.
  • Energy is released during recombination, which is emitted in the form of a photon.
  • This process is called electroluminescence.
  • The emitted power is proportional to the forward current during
    operation.
  • Color emitted depends on band gap
47
Q

What are the voltages / wavelengths corresponding to the different color LEDs

A

IR - 1.3 - 930
red - 1.8 - 650
yellow - 2.2 - 590
green - 2.4 - 570
blue - 3.5 - 470
white - 3.5

48
Q

What are the applications of LEDs?

A
  • Lighting of all kinds
  • Radiation of infrared light in sensor technology
  • Generation of UV radiation in medical applications
  • Signal generation in optical fibers
49
Q

What is a photodiode?

A

Produces current when exposed to light

50
Q

What are the applications of photodiodes?

A
  • Galvanic Isolation
  • High Voltage transmission
  • Displays
51
Q

What are passive components?

A

Resistors, capacitors, inductors

52
Q

What are transistors used for?

A

To switch and control electrical voltages

53
Q

What are the two designs of transistors?

A
  • Bipolar Junction Transistor
  • Field Effect Transistor
54
Q

What are the three ports of BJT?

A

Base, collector and emitter

  • The base port is the control port
55
Q

What are the two types of BJTs?

A
  • n-p-n
  • p-n-p
56
Q

Where do diodes face in npn and pnp diodes?

A

Inwards for pnp and outwards for npn

57
Q

What are the three ways a bipolar transistor can be operated?

A

Emitter circuit
Collector circuit
Base Circuit

58
Q

How can a transistor be used in an Emitter circuit?

A

Connect control voltage to collector and emitter. To make the transistor conductive provide voltage greater than diffusion voltage between the base and the emmiter.

59
Q

What region should a BJT transistor be operated in?

A

Saturation region

60
Q

What three areas can the output characteristic field for BJT be divided in?

A

Saturation area

Linear Area

Breakthrough Area

61
Q

What is the main characteristic of the BJT?

A

Multiplication of base current with the collector current. In normal operation I_B is much smaller than I_C

62
Q

What is the gain factor?

A

/beta = (dI_C)/(dI_B)

typical values of beta are 10-250

63
Q

What are the three terminals of the MOSFET?

A

Gate, drain and source

64
Q

what is MOSFET?

A

Metal oxide field effect transistor

65
Q

What are the three circuits for mosfet?

A

Source (=emitter)

Drain(=collector)

Gate(=base)

66
Q

What are the two types of MOSFETS?

A

n and p type mosfets

67
Q

What is the structure of the MOSFET?

A

three doped regions of different types

a gate connecting the two similarly doped regions via an insulator

68
Q

What happens when a voltage is applied to the MOSFET gate?

A

the insulated connection affects the electric field between drain and source, allowing or preventing current flow

69
Q

What kind of power output is required for MOSFET at low frequencies?

A

Very low power

70
Q

What are the three ranges for the MOSFET characteristic curve?

A
  • Ohmic/triode 1
  • Saturation 2,3
  • Breakdown 4
71
Q

What are IGBTs?

A

Insulated gate bipolar transistors

72
Q

What are the three terminals of IGBTs?

A

Collector, gate, emmiter

73
Q

What is the advantage of IGBTS?

A

Combines the advantages of the BJTs (high reverse voltage and low forward resistance) and MOSFETs (little power required for driving)

74
Q

What are good applications of IGBTs

A

High power, high voltage, and high current

75
Q

What does the structure of an IGBT consist of?

A

A Darlington circuit of a pnp BJT and an n-channel MOSFET

76
Q

When is a Darlington circuit used?

A
  • The Darlington circuit is used when very large currents are to be
    switched with low powers
77
Q

How is the IGBT controlled?

A

The IGBT is controlled via the gate of the MOSFET: If the gate emitter voltage UGE exceeds the threshold voltage, current flows
across the BJT

78
Q

What are the operational ranges of the characteristic ranges of the IGBT

A

Reverse blocking range

Linear

Active range

79
Q

Does the IGBT or MOSFET have greater safe operating range?

A

IGBT

80
Q

What are some new wide band gap semiconductor materials?

A

Silicon carbide and gallium nitride

81
Q

What is the order of band gap?

A

Si < SiC < GaN

82
Q

What is the order of critical field?

A

Si < SiC < GaN

83
Q

What is the order of electron mobility?

A

SiC< Si < GaN

84
Q

What is the order of electron saturation?

A

Si < SiC < GaN

85
Q

What is the order of thermal conductivity?

A

GaN < Si < SiC

86
Q

What are application possibilities of SiC?

A
  • SiC photodiodes: Sensitive to UV light.
  • SiC MOSFETs: Low on-resistance, smaller cooling surfaces. Lower
    switching times enable precise results with lower radiation loads, e.g.
    in medical imaging technology.
87
Q

What are application possibilities for GaN?

A
  • GaN-HEMT (High-Electron Mobility Transistor): For high-frequency
    applications due to low gate capacitance, thus enabling smaller passive components.
  • 48 V DC/DC converter: Currently used for 5G infrastructure, AI applications and LIDAR systems due to stable power supply, high power
    density and high switching frequencies at low cost.
88
Q
A

Electrical Engineering (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions