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Flashcards in Semiconductor Physics Deck (27)
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1

What was a major advantage of transistors, compared to devices of the past ?

There was no need for heat, or vacuum for electrons to flow

2

How can conductivity of conductors be explained with respect to energy bands ?

The valence band is partially filled or
Overlaps with conduction band

3

What happens when electrons jump into a higher energy level due to heat ?

Random motion for the electrons

4

What happens when it is due to an electric field ?

The electrons move in a direction opposite to the field

5

What is the nature of the valence and conduction band in insulators ?

Valence band - Completely filled
Conduction band - Completely empty

6

What is the order of the energy gap in between the valence and conduction band in insulators ?

5 eV

7

What is the thermal energy possessed by an electron at a given temperature T ?

KT,
K is Boltzmann constant

8

Why do insulators not conduct electricity at room temperature ?

KT is very much below the band gap at room temperature

9

What is dielectric breakdown ?

The phenomenon that occurs when an insulator starts conducting electricity

10

How does this happen ?

By applying a sufficiently large voltage

11

What is the energy band gap in semi conductors ?

About 1 eV

12

What is the band gap for pure Silicon ?

1.1 eV

13

What is the band gap for pure Germanium ?

0.72 eV

14

What is doping ?

The process of adding a small amount of impurity to a semi conductor

15

Why is this done ?

To increase conductivity

16

What is the impurity called ?

Dopant

17

What is an intrinsic conductor ?

A pure semiconductor

18

How does an intrinsic conductor conduct electricity ?

Thermal excitation only

19

What is an extrinsic conductor ?

A conductor, containing a small amount of impurity

20

What are the two types of extrinsic conductors ?

N- Type
P - Type

21

What is the law of mass action ?

The product of charge carrier concentration remains constant

22

What kind of semiconductors does this apply to ?

Both extrinsic and intrinsic

23

Does the law of mass action vary with doping ?

No, the product remains the same even with variation in doping

24

When is Lorentz force experienced and by what ?

It is experienced by a moving charge when it is subjected to the influence of a magnetic field

25

What is hall effect ?

When a current carrying body is subjected to a perpendicular magnetic field, a mutually perpendicular electric field is induced

26

What are the applications of Hall Effect ?

Determination of charge carrier concentration, charge mobility

27

What else can Hall Effect tell us about a conductor ?

Whether it's n-type or p-type