Semiconductors are materials that are neither good electrical conductors or insulators. They are one of the most important enabling technologies for digital computers. Semiconductors are the foundation of all modern electronic devices which use circuitry. These materials were first introduced to computing to solve issues related to vacuum tubes used in analogue computers. Not all semiconductors are good for use in computers. Those that are used in computers must be carefully manufactured to create desirable properties. Materials scientists are hard at work developing new semiconductor materials for use in computers. Electrical engineers are also working to design new semiconductor devices to improve computer performance.
Why Use Semiconductors in Computers?
Semiconductors were first introduced to computers to solve common problems in analogue computing devices. Most of these problems were related to vacuum tubes, a fundamental component of analogue computers. The tubes would often leak, and the metals used to transmit electrons within them would frequently burn out. Semiconductors did not suffer these issues. Semiconductor materials conduct electrons in an entirely different manner than metals, causing them to avoid burn out. Unlike vacuum tubes, semiconductors did not need to warm up over long periods of time prior to use. Additionally, they required far less space than a series of vacuum tubes. The first semiconductor based transistor was made in 1947. The first integrated circuit based on semiconductor technology followed shortly after, in 1959.
Semiconductor Materials Used in Computers
Not all semiconductors are suitable for use in computers. The material which has become the standard semiconductor for circuitry is silicon. Silicon is the most abundant element in the earth's crust, and is accessible from almost anywhere on earth. This makes silicon inexpensive, driving down the cost of computers and other technological devices. Some computers use other semiconductor materials to achieve faster electron conduction speeds. An example is germanium with a small concentration of arsenic impurities. While this material achieves faster conduction rates, its cost is significantly higher than silicon.
Manufacturing Semiconductors for Use in Computers
Semiconductor materials like silicon can only be used in computers if they demonstrate a good range of properties, which require high purity semiconductor materials. Making these materials entails the use of specialised manufacturing processes. Pure silicon wafers are cut from giant crystals which are artificially grown in furnaces at elevated temperatures. These crystals are free from impurities which would damage the desirable properties of the semiconductor material. Once the crystal has been grown into a sizeable ingot, thin wafers are sliced, polished, and cleaned. One of the reasons why the cost of computers continues to decline is a continued effort to improve the manufacturing process of semiconductor materials.
Scientists are constantly looking for ways to improve semiconductors used in computers. Materials scientists seek ways to improve materials properties directly. For example, it is now common to add small concentrations of impurity ions to increase conduction rates. Electrical engineers try to use semiconductors in new ways to improve computing performance. Altering the shape of semiconductor devices could reduce heat generated inside computer parts, enabling faster and more efficient computers. Researchers must balance improvements to performance with cost increases when considering what's practical for everyday use.