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晶体管的工作原理

How Does a Transistor Work?

In this phone, there are nearly 100 million transistors,
这部手机有近1亿个晶体管
in this computer there’s over a billion.
这台电脑有超过10亿个晶体管
The transistor is in virtually every electronic device we use:
我们使用的所有电子设备中几乎都有晶体管
TV’s, radios, Tamagotchis.
电视机 收音机 电子宠物
But how does it work?
那它的工作原理是什么呢?
Well the basic principle is actually incredibly simple.
嗯 其实基本原理非常简单
It works just like this switch, so it controls the flow of electric current.
它的工作原理就像这个开关 用于控制电流
It can be off, so you could call that the zero state
它可以断开 可以叫做0状态
or it could be on, the one state.
也可以闭合 叫做1状态
And this is how all of our information is now stored and processed,
我们所有的信息就是以这种方式存储和处理
in zeros and ones,
用0和1表示
little bits of electric current.
即电流的二进制表示法
But unlike this switch, a transistor doesn’t have any moving parts.
但与开关不同的是 晶体管没有任何活动部件
And it also doesn’t require a human controller.
也不需要人力控制
Furthermore, it can be switched on and off
此外 它的开关速度
much more quickly than I can flick this switch.
比我按下这个开关要快得多
And finally, and most importantly it is incredibly tiny.
最后 也是最重要的一点 它极其微小
Well this is all thanks to the miracle of semiconductors
嗯 这一切都要归功于半导体奇迹
or rather I should say the science of semiconductors.
或者 我应该说是半导体科学
Pure silicon is a semiconductor,
纯硅是一种半导体
which means it conducts electric current better than insulators
这意味着它的导电性比绝缘体更强
but not as well as metals.
但不如金属
This is because an atom of silicon has four electrons in its outermost or valence shell.
这是因为一个硅原子的最外层或价层有4个电子
This allows it to form bonds with its four nearest neighbours.
因此 它能与周围的4个硅原子形成共价键
-Hidey ho there! -G’day.
-Wasaaaaap!?
-嗨 各位! -你好
-干嘛呢!?
So it forms a tetrahedral crystal.
所以就形成了一个四面体晶体
But since all these electrons are stuck in bonds,
但是 由于所有电子都被束缚在共价键中
few ever get enough energy
很少有电子能获得足够的能量
to escape their bonds and travel through the lattice.
挣脱共价键的束缚并在晶格中自由移动
So having a small number of mobile charges is what makes silicon a semi-conductor.
硅有少量的移动电荷 所以硅是半导体
Now this wouldn’t be all that useful without a semiconductor’s secret weapon —
如果没有半导体的秘密武器——掺杂
doping.
那就不会起作用了
You’ve probably heard of doping,
你可能听说过掺杂(兴奋剂)
it’s when you inject a foreign substance in order to improve performance.
即掺入某种杂质以改善性能的过程
Yeah it’s actually just like that, except on the atomic level.
没错 其实就像那样 只不过是原子层面
There are two types of doping called n-type and p-type.
掺杂有两种类型 分别叫做n型和p型
To make n-type semiconductor, you take pure silicon
n型半导体是在纯硅中
and inject a small amount of an element with 5 valence electrons,
掺杂少量带有5个价电子的元素
like Phosphorous.
比如磷
This is useful because Phosphorous is similar enough to silicon
因为磷和硅非常相似 所以可以掺杂
that it can fit into the lattice, but it brings with it an extra electron.
磷可以融入硅晶格 但会多出一个电子
So this means now the semiconductor has more mobile charges
这意味着半导体现在有更多的移动电荷
and so it conducts current better.
因此 它的导电性更强了
In p-type doping,
在p型掺杂中
an element with only three valence electrons is added to the lattice.
在硅晶格中掺杂了一种只有3个价电子的元素
Like Boron.
比如硼
Now this creates a ‘hole’ —
那就形成了一个“空穴”
a place where there should be an electron, but there isn’t.
这里本该有一个电子 但是没有
But this still increases the conductivity of the silicon
但这仍然可以提高硅的导电性
because electrons can move into it.
因为电子可以移动到空穴
Now although it is electrons that are moving,
尽管是电子在移动
we like to talk about the holes moving around —
但我们倾向于称之为空穴的移动
because there’s far fewer of them.
因为空穴的数量更少
Now since the hole is the lack of an electron,
由于空穴缺少了一个电子
it actually acts as a positive charge.
它实际上就充当了一个正电荷
And this is why p-type semiconductor is actually called p-type.
这就是p型半导体实际上被称为p型的原因
The p stands for positive —
p代表正电
it’s positive charges, these holes, which are moving and conducting the current.
这些空穴相当于正电荷 自由移动并导电
Now it’s a common misconception that n-type semiconductors are negatively charged
那么 就有一个常见的误解 认为n型半导体带负电
and p-type semiconductors are positively charged.
p型半导体带正电
That’s not true, they are both neutral
这是错的 这两种半导体都呈电中性
because they have the same number of electrons and protons inside them.
因为它们内部的电子数和质子数相同
The n and the p actually just refer to the sign of charge that can move within them.
其实 n和p只是表示它们内部可以移动的电荷的符号
So in n-type, it’s negative electrons which can move,
因此 在n型半导体中 可以移动的是负电子
and in p-type it’s a positive hole that moves.
而在p型半导体中 移动的是正电子
But they’re both neutral!
但这两种半导体都是中性的!
A transistor is made with both n-type and p-type semiconductors.
一个晶体管由n型和p型半导体组合而成
A common configuration has n on the ends with p in the middle.
一种常见的配置是 n型在两端 p型在中间
Just like a switch,
就像开关一样
a transistor has an electrical contact at each end
晶体管的两端各有一个电触头
and these are called the source and the drain.
分别称作源极和漏极
But instead of a mechanical switch, there is a third electrical contact called the gate,
它没有机械开关 而是有另一个叫做栅极的电触头
which is insulated from the semiconductor by an oxide layer.
栅极通过氧化层与半导体绝缘
When a transistor is made, the n and p-types don’t keep to themselves —
晶体管制成时 n型和p型半导体并不自成一体
electrons actually diffuse from the n-type,
实际上 自由电子会从电子密度大的n型半导体
where there are more of them into the p-type to fill the holes.
扩散到p型半导体以填补空穴
This creates something called the depletion layer.
这就产生了所谓的耗尽层
What’s been depleted?
耗尽了什么呢?
Charges that can move.
可以移动的电荷
There are no more free electrons in the n-type — why?
n型半导体没有了多余的自由电子 为什么?
Because they’ve filled the holes in the p-type.
因为它们都填补到p型半导体的空穴了
Now this makes the p-type negative thanks to the added electrons.
现在 p型半导体由于电子增多 呈负电性
And this is important because the p-type will now repel any electrons
这很关键 因为p型半导体会排斥
that try to come across from the n-type.
任何试图从n型半导体过来的电子
So the depletion layer actually acts as a barrier,
因此 耗尽层实际充当了一个屏障
preventing the flow of electric current through the transistor.
阻止电流通过晶体管
So right now the transistor is off, it’s like an open switch, it’s in the zero state.
现在晶体管是断开状态 就像断开的开关 处于0状态
To turn it on, you have to apply a small positive voltage to the gate.
要闭合它 就必须在栅极上施加一个小正电压
This attracts the electrons over
这会把电子吸引过来
and overcomes that repulsion from the depletion.
并克服来自耗尽层的排斥力
It actually shrinks the depletion layer
其实也会使耗尽层缩小
so that electrons can move through and form a conducting channel.
从而 电子能够通过并形成一个导电通道
So the transistor is now on, it’s in the one state.
现在 晶体管是闭合的 处于1状态
This is remarkable
太了不起了
because just by exploiting the properties of a crystal
因为仅仅通过利用晶体的特性
we’ve been able to create a switch that doesn’t have any moving parts,
我们就能够创造出一个没有任何活动部件的开关
that can be turned on and off very quickly just with a voltage,
它只需一点电压就可以非常迅速地闭合和断开
and most importantly it can be made tiny.
最重要的是 我们可以把它做得非常微小
Transistors today are only about 22nm wide,
今天的晶体管大约只有22nm宽
which means they are only about 50 atoms across.
也就是说只有大约50个原子宽
But to keep up with Moore’s law, they’re going to have to keep getting smaller.
但是为了遵守摩尔定律 晶体管必须继续缩小
Moore’s Law states
摩尔定律指出
that every two years the number of transistors on a chip should double.
每两年 一个芯片上的晶体管数量应该翻一番
And there is a limit
但这是有极限的
as those terminals get closer and closer together,
当两端越靠越近
quantum effects become more significant
量子效应就越显著
and electrons can actually tunnel from one side to the other.
那么 电子实际上可以从量子隧道一端穿到另一端
So you may not be able to make a barrier high enough to stop them from flowing.
那我们就可能无法制造出足够高的屏障来阻止电子流动
Now this will be a real problem for the future of transistors,
这将是未来晶体管要面临的一个大问题
but we’ll probably only face that another ten years down the track.
可能得十年后吧
So until then transistors, the way we know them, are going to keep getting better.
因此 在那之前 我们所认知的晶体管将会越来越好
Once you have, let’s say, three hundred of these qubits,
当有比如300个这样的量子比特
then you have like two to the three hundred classical bits.
那么就有2的300次方个经典比特
Which is as many particles as there are in the universe.
也就是宇宙中所有的粒子数

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视频概述

本视频生动形象地介绍了晶体管的工作原理,简单易懂。

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视频来源

https://www.youtube.com/watch?v=IcrBqCFLHIY

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