Boron-doped single-crystal diamond has broad development prospects in the application of high-temperature and high-power

Diamond is a structural form of carbon. In a diamond crystal, each carbon atom has 4 nearest-neighbor carbon atoms and 12 next-nearest-neighbor carbon atoms. There are 8 atoms in one unit cube. Since the atomic radius of boron is smaller than that of carbon, boron can easily enter the lattice of the diamond crystal. Boron can exist in three possible forms within the diamond crystal: the first is that boron atoms replace the positions of carbon atoms; the second is that boron atoms are located between carbon atoms; the third is that boron atoms can also fill in defects occurring during the growth of the diamond crystal, especially surface defects. All these forms will have an impact on the properties of the diamond crystal.

The crystal structure of diamond is a typical atomic lattice, in which there are no free electrons, making it non-conductive. Ordinary diamond is an insulator not only because it has 4 valence electrons, but also because its band gap is very large, about 5.5 electron volts. Practice has proved that trace chemical impurities can control the conductivity of semiconductors. For example, adding boron to silicon at a ratio of 1 boron atom to 10⁵ silicon atoms increases the conductivity by 10³ times at room temperature, because boron, a typical trivalent impurity, can capture electrons from the valence band and leave holes behind. When boron atoms are introduced into the diamond crystal, its energy band state will change. Since boron has only 3 outer electrons, it always lacks 1 electron when forming covalent bonds, creating a negatively charged center and thus a hole. The introduction of boron atoms greatly increases the number of holes, so its conductivity is significantly enhanced.

For pure diamond, due to the absence of freely moving electrons inside it and its wide band gap of 5.5 eV, it has a very high resistivity and can serve as an excellent electrical insulator. However, when group Ⅲ or group Ⅴ elements are doped into diamond, diamond can be transformed from an insulator into a semiconductor or even a conductor. When boron atoms (which have three valence electrons) enter the diamond lattice, they replace carbon atoms in a substitutional manner to become acceptor centers, generating hole carriers in the lattice. As a result, the diamond becomes a p-type semiconductor, and this type of doping is referred to as p-type doping. With the increase in boron content, the electrical conductivity of diamond increases. It has broad development prospects in the application of high-temperature and high-power electronic devices.

The boron-doped single-crystal diamond produced by CSMH can achieve doping from low concentration to high concentration. It has realized a uniform and controllable concentration and a customizable boron doping process.CSMH uses the MPCVD method to prepare large-sized and high-quality diamonds,and currently has mature products such as diamond heat sinks, diamond wafers, diamond windows,diamond hetero junction integrated composite substrates,etc.