How do semiconductor materials develop? What are their characteristics?

Some common semiconductor materials include silicon, germanium, gallium arsenide, and indium phosphide. While silicon is the most widely used material in integrated circuits due to its low cost and abundance (approximately $2 per kilogram), it has a relatively low operating frequency limit of only a few tens of GHz. Germanium, on the other hand, has a faster conductivity increase with temperature than silicon but comes at a higher price point of about $2 per gram. Gallium arsenide, with an electron mobility of 8500cm2 VS2, is commonly used in high-frequency and high-speed electronic devices; however, it can be quite expensive at approximately $300 per gram. The band gap of indium phosphide makes it a popular choice for optoelectronic devices, but its cost can reach up to $1,000 per gram. Ultimately, the selection of a semiconductor material depends on the specific needs and budget of the application as various factors such as performance and cost must be carefully considered.

Semiconductor materials commonly used

Semiconductor element

Si (silicon)

Silicon is the most commonly used semiconductor material and it is widely used in integrated circuits and solar cells. The purity of silicon is very high and usually needs to reach more than 99.9999%. As the temperature increases, silicon conductivity increases as more electrons are excited to the conduction band. At room temperature, silicon has a band gap width of 1.1 eV, which makes it a good semiconductor.

Ge (Germanium)

Due to its small band gap (0.66 eV) and high leakage current at room temperature, germanium has been replaced by silicon in some applications. However, germanium still has advantages in some high-speed applications. As temperatures increase, the conductivity of germanium increases, but at a faster rate than silicon.

Semiconductor composite

Gallium arsenide (GaAs)

As a composite semiconductor material, gallium arsenide is widely used in electronic devices with high frequencies and high speeds. GaAs has a higher electron mobility compared to silicon, which gives it an advantage in high-frequency applications. The band gap in GaAs is 1.43 eV, which reduces thermal noise and increases power output.

Indium phosphate (InP)

Another very important composite development semiconductor is indium phosphide, which is mainly used in the research of optoelectronic devices and high-speed electronic control devices. InP has a band gap of 1.35 eV, which is similar to GaAs, but its electron mobility is higher, which makes it more suitable for enterprise applications. Other countries, including InGaAs, also use indium phosphide as a substrate for semiconductor nanomaterials.

The choice of semiconductor materials depends on specific application requirements and cost considerations, and each semiconductor material has its own unique characteristics and uses. Due to silicon's abundance and cost-effectiveness, even though germanium is superior to silicon in some ways, it is still the most commonly used semiconductor material.

Semiconductor material characteristics

Temperature and conductivity

One notable aspect of semiconductors is their temperature-dependent electrical conductivity, which differs from that of metals. Unlike metals, semiconductors experience an increase in conductivity as temperature rises. This can be attributed to the fact that a higher temperature allows more valence band electrons to gain sufficient energy and transition to the conduction band, resulting in an increase in free electrons and conductivity. For instance, at room temperature, both silicon and germanium exhibit rising conductivity with increasing temperature, but germanium shows a more rapid increase compared to silicon.

Structure of bands

An essential characteristic of semiconductors is their band structure, consisting of two main energy bands: valence and conduction. This energy difference between these bands is referred to as the band gap.

When electrons acquire sufficient energy to transition from the valence band to the conduction band, they can conduct electricity. The width of this band gap plays a significant role in determining important qualities of semiconductors, such as electrical conductivity and optical properties. For instance, silicon has a band gap of 1.1 eV, while germanium has a band gap of 0.66 eV.

Type of carrier

Electrons and holes are the two main conductive carriers in semiconductors. In the conduction band, an electron jumps from the valence band to the negative charge, whereas a hole appears as a positive charge in place of an electron missing from the valence band. The main carrier types in semiconductors can be classified into two types: N-type and P-type. In N-type semiconductors, electrons are the main carriers, while in P-type semiconductors, holes are the main carriers.

As a result of these enterprise characteristics, semiconductor materials are extensively researched and applied in electronic and optoelectronic devices. Further analysis can be obtained by constantly adjusting semiconductor properties, such as doping, to optimize its performance based on its specific application requirements.