Name: nanoHUB-U 納米半導體：半導體基礎知識 (nanoHUB-U Nanotransistors: Semiconductor Fundamentals)
Uploaded: 2021-01-14T06:38:36.000Z
Duration: 43 min
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If you have that basic understanding, you'll be able

to follow the course and, I think, learn some new

and interesting things about nano devices

What I'd like to do in this special lecture is to quickly go

through some highlights of semiconductor physics.

Now, this is material that it takes me five or six weeks to go

My intent is just to quickly review some quick --

some key concepts that we'll be using throughout the course.

If you've seen those before or if there are one or two

that you think, well, maybe I need to refresh my memory

and review that a little more, then you're in good shape.

in this quick summary is completely brand new to you,

then you probably don't have the background that you're going

[Slide 2] So let's take a quick look at some key concepts

These are the seven topics that I'd like to go over.

We're just quickly reviewing what some of the key points are.

Let's begin at a very basic level; silicon atoms.

Silicon is the most common semiconductor used

You'll remember from your freshman chemistry course

which means it has 14 electrons that have to be accommodated

And you might remember from your freshman chemistry

and N equals 2 orbitals hold two electrons.

In P orbitals we have a Px, a Py, and a Pz orbital.

Each one of those can hold two electrons,

So the P orbitals can hold six electrons.

And we just go through and we fill up all the energy levels

until all 14 electrons are accounted for.

And if we do that, we'll find that we fill up the 3S level

and we put two electrons in the 3P level.

But if you look at those uppermost energy levels,

the N equals 3 states, there are eight states there; two S states

And we've used four of those eight states.

The lower states here, lower energy states,

There's not much that we can do to interact with them.

The chemistry in semiconductor physics all has to do

with the valence electrons, so that's what we focus on.

[Slide 4] Now, we're going to take a crystal chunk of silicon

The density of silicon is about 5 times 10

because diamond also crystallizes in this structure.

And the key point is that each atom forms covalent bonds

to four nearest neighbors, with those four valence electrons

that it shares with its four nearest neighbors.

Only the valence electrons are going to be --

in the valence states are going to be important to us.

to the 22nd per cubic centimeter, then we're going

to have 8 times N atoms states in this solid that are going

But when we put these atoms very closely together

the electron wave functions overlap and things change.

[Slide 5] Energy levels become energy bands.

So if we just look at those valence electrons,

the four electrons in the eight states, if we put them

in a silicon crystal the energy levels are going to broaden

and smear out into a range of energy bands.

And what we'll find if we do the quantum mechanics properly is

We call that the valence band of energies.

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nanoHUB-U 納米半導體：半導體基礎知識 (nanoHUB-U Nanotransistors: Semiconductor Fundamentals)

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