Tip & How-To about Computers & Internet

Silicon (Part 1)

Silicon is the base material in a great deal of computing equipment. It has been used extensively for decades and is a material that Engineers and Scientists understand well and can easily manipulate. Advances in this manipulation has led to both increased speed and reduced size of complex computing equipment. In this article, I'll explain how silicon is used in computers and in the next couple of articles I'll talk about some potential replacements for silicon and the benefits and drawbacks of each of them.
In computer chips and transistors silicon is known as a semi-conductor. But silicon by itself is not a semi-conductor; in fact it's an insulator. This is due to the chemical structure of the element Silicon. Silicon has 4 valence electrons (outer electrons that can participate in the forming of bonds with other atoms), this allows silicon atoms to form strong covalent bonds with other silicon atoms with no free electrons as a result of the bond. This means that when electricity is applied to silicon there is no way for it to travel through the material, because there are no free electrons.
A covalent bond is a special chemical bond between atoms formed when the atoms share one or more outer electrons.
So how can silicon be used as a conductor? Silicon can become a semi-conductor through a process known as doping. There are two kinds of doping used. The first kind is referred to as N-type. In this type of doping either phosphorous or arsenic is added in very small quantities to the silicon. Both phosphorous and arsenic have 5 outer electrons so when they form covalent bonds with silicon atoms there becomes a free electron. Even a small amount of phosphorous or arsenic can produce enough free electrons for silicon to become a semi-conductor. These free electrons will give the doped silicon a negative charge; that's why this type of doping is called N-type.
Another type of doping is called P-Type. In this type of doping either boron or gallium is used to bond with silicon. The difference with this type of doping is that boron and gallium each have three outer electrons. So, when the covalent bonds are formed with silicon atoms there is a 'hole' that is formed. This absence of an electron gives the effect of a positive charge (hence the 'P-type' name) which is really the opposite of the N-type doped silicon.
By themselves these doped silicon semiconductors are not that special. However, when we put them together interesting things can happen. In figure 1, there is a P-type silicon block next to an N-type silicon block. At first glance this might look a little weird. We have what looks very much like positive and negative charges next to each other - wouldn't the electrons travel to the positive side to balance out the charges?


Figure 1: P-type and N-type silicon forming a diode
No. The electrons of the N-type silicon will not travel to the P-type silicon to balance out the charges. This is because of the band gap. By itself the amount of charge is not high enough to encourage mobility of the electrons. This band gap allows us to do some amazing things with the doped silicon.
If we put N-type silicon next to P-type silicone and combine them with a power source we can make a diode. A diode is a basic electronic device that allows electricity to flow in only one direction - the direction that supplies energy greater than the band gap of the doped silicon. Figure 2 shows the P-type and N-type silicon together in a circuit with a power source. When the power source is in the right direction electricity will flow through the diode, when it is in the wrong direction electricity will not flow.


Figure 2: a diode connected to a power source
It's worth noting here that if the power source is large enough, then the diode will fail and electricity will flow in either direction. This is because there is also a band gap in the opposite direction, while it requires a much greater amount of energy to surpass the band gap, it is not infinite.
Diodes are a very simple, yet highly valuable and often used electronic component. However, one of the most important electronic components made with silicon is the transistor. To make a transistor with doped silicon we can combine the doped silicon into a sandwich of sorts. These types of transistors are called "Junction Transistors", and there are two kinds of these junction transistors. There is an NPN kind which has P-type silicon sandwiched between two N-type silicon pieces. There is also the PNP type of junction transistor which has N-type silicon sandwiched between two P-type silicon pieces. These two types of junction transistors are basically the same except that they operate with the reverse polarity of the other.
So to consider how this works, let's just examine the NPN type junction transistor. If you remember when I was explaining the diodes you might think that this looks like two diodes back to back which would stop electricity from flowing in either direction - you'd be right. However, if we apply a small electrical current to the middle P-type silicon (often referred to as the 'base') we can allow current to flow from one N-type silicon (often referred to as the 'collector') to the other N-type silicon (often referred to as the 'emitter'). Likewise if we remove the electrical current from the base the current from collector to emitter will stop. This type of action allows us to use this junction transistor as a simple switch. It is simple switches like this that we can combine together to form more complex logical gates.

Figure 3: a diagram of an NPN junction transistor
Another type of transistor we can make with doped silicon is called a Field Effect Transistor or a FET. There are a couple of subtypes of FET transistors, but they each work basically the same way. In a FET transistor only two types of doped silicon are used, and N-type and a P-type. This type of transistor takes advantage of the magnetic field created along with any current. Basically a FET transistor will allow electricity to flow through one type of silicon which is used as the channel. When electricity is applied to the other type of silicon a magnetic field is produced which interferes with the current flowing through the channel thus significantly reducing it. By utilizing this magnetic field effect we can use the FET as a switch in much the same way as I explained we could use the junction transistor as a switch.
So that's a simplified explanation of how silicone is used in electronic components, including computer chips and processors of all sorts. You can see how improving the electrical performance characteristics and decreasing the size of these components can have dramatic effects on the performance and size of the finished computer parts. However, as you reduce the size of silicone enough the physical properties start to change, making it more difficult to achieve the desired results. In my next article I'll discuss this along with some alternatives to silicon that are currently being explored.

Posted by on

Computers & Internet Logo

Related Topics:

Related Questions:

2 Answers

How about Fuzhou Antyco Optics CO., Ltd?


Fuzhou Antyco Optics Co., Ltd. is a professional manufacturer of crystal and optical components in the photonics industry. Antyco owns standard factory, advanced fabricating machine including Spherical Milling Machines, CNC Plano Milling, High speed Polishing, Precision Polishing, CNC Grinding and Polishing, Coating Machine, Ultrasonic Cleaner, etc.. The strong and steady growth have lead us to a very skilled team of fabricators, mechanical engineers, process engineers, optical engineers and coating designers, which successfully provided the advanced technical solutions and satisfactory products for different areas of the numerous customers.
Our manufacturing capabilities consist of all types of customized lens, Beam Splitters, Polarizing Optics, Prisms, Filters, Coatings, Optical Systems, Optical Assemblies and Optical Systems Solutions, Laser Crystals, NLO Crystals. The products are widely used in laser industry, optical communication, laser display, medical equipment, survey equipment, precision Instrument and semiconductor. Optical elements of various materials can be processed in Antyco: zinc selenide(ZnSe), zinc sulfide(ZnS), calcium fluoride(CaF2), barium fluoride(BaF2), silicon(Si), germanium(Ge), YAG crystals, YVO4, sapphire, quartz glass, optical glass, ceramics, cooper, aluminum, etc.
with the strict quality management system, Antyco got the ISO 9001:2000 Certificate. Today, over 60% of Antyco products are exported to USA, Japan, Germany and other European, Asian Market. Looking ahead, Antyco will continue to deliver customers with reliable quality, competitive price and on-time delivery products.

For more: http://antyco.com/

Sep 26, 2016 | 2007 Toyota Camry

3 Answers

What is silicon dioxide?


Silicon dioxide also known as silica. It is a natural compound made of two of the earth's most abundant materials,the earth's crust is 59% silica. It is naturally found in water,plants,animals and within the earth. Silicon dioxide serves as an anticaking agent, research says silicon dioxide found in plants and water it is safe.

Feb 19, 2016 | Coffee Makers & Espresso Machines

1 Answer

Thread fraying on certain vinyl material, why?


u need a silicon based nylon thread and a larger needle. needle may be getting hot too depending on thickness of work. spray some silicon on upper thread.

Jan 30, 2013 | Juki DDL-8300

2 Answers

how the microprocesser function


Features
  • Microprocessors have become the movers and shakers of our everyday world. We use them in computers, televisions, watches, microwaves and practically every other electronic device. Their micro-size is no reflection of the myriad capabilities these chips possess, ranging from 2 to 3 mm square to maybe an inch thick. Silicon makes up the material of a microprocessor chip. Sliced wafer thin, silicon serves as an ideal conductor and insulator for Function
  • A microprocessor is the central processing unit in a computer. It receives, transmits and coordinates every command and process carried out by the system. Electrical currents, moving through wires and transistors, are converted into usable messages through the use of a Boolean logic language. Based on the "on/off" frequency of current moving through transistor circuits, this Boolean logic communicates system commands to and from receiving devices within the computer. The microprocessor communicates within two primary capacities: logic and the processing of information. These processes are handled by two components within the chip:
    *Arithmetic logic unit (ALU), responsible for all commands requiring an arithmetic or logic function
    * Control unit (CU), which handles the information processing from the computer's memory
  • From these units within the chip, clusters of wires called "bus" lines send and receive information to and from system devices.
  • Oct 16, 2009 | Computers & Internet

    Not finding what you are looking for?

    929 people viewed this tip

    Ask a Question

    Usually answered in minutes!

    Top Computers & Internet Experts

    Doctor PC
    Doctor PC

    Level 3 Expert

    7733 Answers

    kakima

    Level 3 Expert

    102366 Answers

    David Payne
    David Payne

    Level 3 Expert

    14161 Answers

    Are you a Computer and Internet Expert? Answer questions, earn points and help others

    Answer questions

    Loading...