文章目录
To understand how diodes, transistors, or any integrated circuit work, you must first study the semiconductor – a material that is neither a conductor nor an insulator.
Before knowing the semiconductor, let’s understand what makes a material either a conductor or an insulator.
[!NOTE]
要了解二极管、晶体管或任何集成电路的工作原理，你必须首先研究半导体——一种既不是导体也不是绝缘体的材料。
在了解半导体之前，让我们先了解是什么使材料成为导体或绝缘体。
Conductor（导体）
We all know that copper is a good conductor. The reason is obvious when we look at its atomic structure.
[!NOTE]
我们都知道铜是良导体。当我们观察它的原子结构时，原因是显而易见的。
The nucleus of a copper atom has 29 protons (positive charge). 29 electrons (negative charge) revolve around the nucleus. There are 2 electrons in the first orbit, 8 electrons in the second, 18 in the third and 1 electron in the outer orbit.
In electronics, all that matters is the outer orbit, as it determines the conductivity of the atom. It is also called valence orbit.
[!NOTE]
铜原子核有 29 个质子（带正电荷），29 个电子（负电荷）围绕原子核旋转。第一轨道上有 2 个电子，第二轨道上有 8 个，第三轨道上有 18 个，外轨道上有 1 个电子。
在电子学中，最重要的是外轨道，因为它决定了原子的导电性。它也被称为价轨道。
Net Charge（净电荷）
To find the net charge of an atom, we define the core of an atom as the nucleus and all the inner orbitals.
The core of a copper atom has a nucleus (+29 protons) and the first three orbits (-28 electrons). That’s why the core of a copper atom has a net charge of +1 (+29 of protons -28 of electrons)
Following figure illustrates the core and the valence orbit of a copper atom.
[!NOTE]
为了计算原子的净电荷，我们将原子的核心定义为原子核和所有内轨道。
铜原子的核心有一个原子核（+29 个质子）和前三个轨道（-28 个电子）。这就是为什么铜原子的核心净电荷为 +1（+29 个质子 -28 个电子）。
下图显示了铜原子的核心和价轨道。
Free Electrons（自由电子）
Because the core has a net charge of only +1, the attraction between the core and the valence electron is very weak. Even a nominal voltage can easily dislodge this electron from a copper atom and cause it to flow through the material. This is why the valence electron is often called a Free electron. And the flow of these free electrons is called Current.
Number of free electrons in copper, as in other metals, is what makes it a good conductor of electricity.
[!NOTE]
因为核心的净电荷只有 +1，所以核心和价电子之间的吸引力非常弱。即使是标称电压也可以很容易地将这个电子从铜原子中移出，并使其流过材料。这就是为什么价电子通常被称为自由电子。这些自由电子的流动被称为电流。
铜和其他金属一样，自由电子的数量使其成为电的良导体。
Insulators（绝缘体）
Neon is an example of a best insulator. Let’s look at its atomic structure.
[!NOTE]
氖是最好的绝缘体的一个例子。让我们看看它的原子结构。
A neon atom has 10 protons and 10 electrons. The first orbit contains two electrons and the remaining eight electrons are in the valence orbit.
The core of a neon atom has a net charge of +8 because it contains 10 protons in the nucleus and 2 electrons in the first orbit. Following figure shows the core diagram of a neon atom.
[!NOTE]
一个氖原子有 10 个质子和 10 个电子。第一个轨道包含两个电子，其余八个电子在价轨道上。
氖原子的核心净电荷为 +8，因为它在原子核中包含10个质子，在第一轨道中包含2个电子。下图显示了氖原子的核图。
Because the core has a net charge of +8, the inward pull felt by the valence electrons is very large. Therefore, due to lack of free electrons, insulators do not conduct.
[!NOTE]
由于核心的净电荷为 +8，价电子感受到的向内拉力非常大。由于缺乏自由电子，绝缘体不导电。
[!NOTE]
If a high enough voltage is applied to an insulator, the force is so great that the valence electrons are literally torn from their atoms. This will cause conduction. In the air you will see it as an arc or flash. In solid materials the heat generated will char the material.
如果对绝缘体施加足够高的电压，那么力会非常大，这将导致价电子会从原子中分离出来。你会看到它在空气中呈弧线或闪光。在固体材料中，产生的热量会使材料烧焦。
Semiconductors（半导体）
A semiconductor is an element that is neither a good conductor nor a good insulator. As you might expect, the best semiconductors have four valence electrons.
Silicon is an example of a semiconductor. Let’s look at its atomic structure.
[!NOTE]
半导体是一种既不是良好导体也不是良好绝缘体的元素。正如您所预料的，最好的半导体有四个价电子。
硅就是半导体的一个例子。让我们看看它的原子结构。
A silicon atom has 14 protons and 14 electrons. The first orbit contains two electrons and the second orbit contains eight electrons. The four remaining electrons are in the valence orbit.
The core of a silicon atom has a net charge of +4 because it contains 14 protons in the nucleus and 10 electrons in the first two orbits. Following figure shows the core diagram of a silicon atom.
[!NOTE]
一个硅原子有 14 个质子和 14 个电子。第一个轨道包含两个电子，第二个轨道包含八个电子。其余四个电子位于价轨道中。
硅原子的核心具有+4的净电荷，因为它的原子核中含有 14 个质子，前两个轨道中含有 10 个电子。下图显示了硅原子的核心图。
The conductivity of the atom depends on the number of valence electrons. When an atom has only one valence electron, it is a best conductor. When an atom has eight valence electrons, the atom is a best insulator.
As you can see a silicon atom has four valence electrons due to which its electrical conductivity falls between that of a conductor and an insulator. This is what makes silicon a Semiconductor.
[!NOTE]
原子的电导率取决于价电子的数量。当原子只有一个价电子时，它是最好的导体。当原子有八个价电子时，原子是最好的绝缘体。
正如你所见，硅原子有四个价电子，因此它的电导率介于导体和绝缘体之间。这就是硅成为半导体的原因。
Silicon Crystals（硅晶体）
When silicon atoms combine to form a crystal, they arrange themselves in a systematic pattern. Each silicon atom shares its valence electrons with four neighboring atoms such that every atom has eight electrons in its valence orbit.
The following figure shows how a silicon atom shares electrons with four neighbors.
[!NOTE]
当硅原子结合形成晶体时，它们会以系统的图案排列。每个硅原子与四个相邻原子共享其价电子，因此每个原子在其价轨道上都有八个电子。
下图显示了硅原子如何与四个相邻原子共享电子。
Covalent Bonds（共价键）
Due to sharing, valence electrons no longer belong to any one atom. These shared valence electrons are pulled by neighboring atoms with equal and opposite forces, causing them to form a bond. We call this type of chemical bond a Covalent bond.
The following figure shows the concept of covalent bonds where each straight line represents one shared electron.
[!NOTE]
由于原子之间共享了价电子，因此价电子不再属于任何一个原子。这些共享的价电子被相邻原子以相等且相反的力拉动，导致它们形成键。我们将这种类型的化学键称为共价键。
下图显示了共价键的概念，其中每条直线表示一个共享电子。
This pulling in opposite directions is what holds the silicon atoms together and gives them solidity.
[!NOTE]
这种相反方向的拉力使硅原子结合在一起，并使其变得坚固。
The Holes（空穴）
At room temperature, the thermal energy in the air causes the atoms in a silicon crystal to vibrate. These vibrations remove the electron from the valence orbit. This free electron starts moving randomly throughout the crystal.
The departure of the electron creates a vacancy in the valence orbit called a hole. This hole behaves like a positive charge because the loss of an electron produces a positive ion.
[!NOTE]
在常温下，空气中的热能会引起硅晶体中的原子振动。这些振动将电子从价轨道中移出。这个自由电子开始在整个晶体中无规律地移动。
电子离开价轨道，会在价轨道上产生一个空位，称为空穴。这个空穴的产生类似于正电荷，因此会产生正离子。
When a free electron enters the immediate vicinity of the hole, it is attracted towards the hole and falls into it. The process of merging a free electron and a hole is called Recombination.
[!NOTE]
当自由电子进入空穴附近时，它被吸引向空穴并落入其中。自由电子和空穴合并的过程称为复合。
Flow of Free Electrons and Holes（自由电子和空穴的流动）
Let’s connect a battery across a pure silicon crystal. Assume that thermal energy has produced a free electron and a hole.
[!NOTE]
让我们将电池连接到纯硅晶体上。假设热能使其产生了自由电子和空穴。
The applied voltage forces free electrons to flow to the left and holes to the right. When free electrons reach the left end of the crystal, they enter the external wire and flow towards the positive battery terminal.
On the other hand, free electrons at the negative battery terminal flow to the right end of the crystal. They enter the crystal and recombine with holes that have reached the right end of the crystal.
[!NOTE]
施加的电压迫使自由电子向左流动，空穴向右流动。当自由电子到达晶体的左端时，它们进入外部导线并流向电池正极端子。
另一方面，电池负极处的自由电子流向晶体的右端，它们进入晶体并与到达晶体右端的空穴重新结合。
In this way, a steady flow of free electrons and holes is established inside the semiconductor.
Free electrons and holes are often called Carriers because they carry a charge from one place to another.
[!NOTE]
通过这种方式，半导体内部建立了自由电子和空穴的稳定流动。
自由电子和空穴通常被称为载流子，因为它们将电荷从一个地方运送到另一个地方。
Doping a Semiconductor（掺杂半导体）
In a pure silicon crystal, each silicon atom uses four valence electrons to bond with its neighboring atoms. This reduces the number of electrons available for conduction. Due to this it acts as an insulator.
[!NOTE]
在纯硅晶体中，每个硅原子使用四个价电子与其相邻原子结合。这减少了可用于导电的电子数量。因此它起到绝缘体的作用。
To increase the number of holes and free electrons in a silicon crystal, and thus to increase its conductivity, it is necessary to dope the crystal.
[!NOTE]
为了增加硅晶体中的空穴和自由电子的数量，从而增加其电导率，有必要对晶体进行掺杂。
Doping is the process of adding impurities to a pure silicon crystal to alter its electrical conductivity. And the impurity that is added is called a Dopant.
[!NOTE]
掺杂是向纯硅晶体添加其它物质以改变其电导率的过程，这些被掺杂其中的物质称为掺杂剂。
The more impurities are added, the greater the number of free electrons and holes, resulting in an increase in conductivity. Meaning, a lightly closed semiconductor has a high resistance, while a heavily doped semiconductor has a low resistance.
[!NOTE]
掺杂的物质越多，自由电子和空穴形成的数量就越多，从而导致导电性增加。这意味着，轻度封闭的半导体具有高电阻，而重度掺杂的半导体具有低电阻。
[!NOTE]
How is a silicon crystal doped?
硅晶体是如何掺杂的？
First a pure silicon crystal is melted. This breaks covalent bonds and transforms silicon from a solid to a liquid. To increase the number of free electrons, pentavalent atoms are added to the molten silicon. And to increase the number of holes, tritant atoms are added. Once it cools down, it turns into a solid crystal structure.
首先将纯硅晶体熔化，这会破坏共价键，使硅从固体转变为液体。为了增加自由电子的数量，将五价原子添加到熔融的硅中。为了增加空穴的数量，将三价原子添加到熔融的硅中。一旦冷却下来，它就会变成固体晶体结构。
n-Type Semiconductor（N 型半导体）
Silicon which is doped to increase the number of free electrons is called n-type semiconductor, where the n stands for negative.
To increase the number of free electrons, pentavalent impurities such as phosphorus, antimony or arsenic are added to silicon. Pentavalent atoms, as the name suggests, have five valence electrons. Following figure shows a phosphorus atom.
[!NOTE]
经过掺杂以增加自由电子数量的硅被称为 N 型半导体，其中 N 代表负。
为了增加自由电子的数量，在硅中添加五价杂质，例如磷、锑或砷。顾名思义，五价原子有五个价电子。下图显示了磷原子。
In n-type semiconductor, a pentavalent atom is in the center, surrounded by four silicon atoms. As we know, a pentavalent atom has five valence electrons. As before, neighboring silicon atoms share four electrons with a pentavalent atom. But this time, there is an extra electron left over (Since valence orbit can hold no more than eight electrons).
[!NOTE]
在 N 型半导体中，一个五价原子位于中心，周围环绕着四个硅原子。我们知道，五价原子有五个价电子。和前面一样，相邻的硅原子与五价原子共享四个电子。但这次，多了一个电子（因为价轨道最多只能容纳八个电子）。
Because each pentavalent atom in a silicon crystal produces one free electron, the resulting doped material has a large number of free electrons.
[!NOTE]
由于硅晶体中的每个五价原子都会产生一个自由电子，因此产生的掺杂材料将具有大量自由电子。
In an n-type semiconductor, as free electrons are greater in number than holes, free electrons are called majority carriers and holes are called minority carriers.
Because the pentavalent impurities donate an extra electron to the silicon crystal, they are often referred to as donor impurities.
[!NOTE]
在 N 型半导体中，由于自由电子的数量大于空穴的数量，因此自由电子被称为多数载流子，空穴被称为少数载流子。
由于五价杂质为硅晶体贡献了一个额外的电子，因此它们通常被称为施主杂质。
p-Type Semiconductor（P 型半导体）
Silicon which is doped to increase the number of holes is called p-type semiconductor, where the p stands for positive.
To increase the number of holes, trialent impurities such as aluminum, boron, or gallium are added to silicon. Trivalent atoms, as the name suggests, have three valence electrons. Following figure shows a boron atom.
[!NOTE]
掺杂以增加空穴数量的硅称为 P 型半导体，其中 P 代表正。
为了增加空穴的数量，在硅中添加三价杂质，例如铝、硼或镓。顾名思义，三价原子有三个价电子。下图显示了硼原子。
In p-type semiconductor, a trivalent atom is in the center, surrounded by four silicon atoms. Since the trivalent atom originally had only three valence electrons and each neighbor shares one electron, only seven electrons are in the valence orbit. This means that a hole exists in the valence orbit of each trivalent atom.
[!NOTE]
在 P 型半导体中，一个三价原子位于中心，周围环绕着四个硅原子。由于三价原子最初只有三个价电子，并且每个相邻原子共享一个电子，因此只有七个电子在价轨道上。这意味着每个三价原子的价轨道上都存在一个空穴。
Because each trivalent atom in a silicon crystal produces one hole, the resulting doped material has a large number of holes.
[!NOTE]
由于硅晶体中的每个三价原子都会产生一个空穴，因此所得的掺杂材料将具有大量的空穴。
In an p-type semiconductor, as holes are greater in number than free electrons, holes are called majority carriers and free electrons are called minority carriers.
A trivalent atom is also called an acceptor atom, because each hole it contributes, can accept a free electron during recombination.
[!NOTE]
在 P 型半导体中，由于空穴的数量大于自由电子的数量，空穴被称为多数载流子，自由电子被称为少数载流子。
三价原子也称为受体原子，因为它形成的每个空穴在重组过程中都可以接受一个自由电子。