The Doping of Semiconductors

The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors.

P- and N- Type Semiconductors

N-Type Semiconductor

The addition of pentavalent impurities such as antimony, arsenic or phosphorus contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor. Phosphorus may be added by diffusion of phosphine gas (PH3). 加入如锑、砷或磷这样的五价杂质，会贡献自由电子，显著提高本征半导体的导电性。磷可以通过磷化氢气体（PH3）的扩散来添加。

P-Type Semiconductor

The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor creates deficiencies of valence electrons, called "holes". It is typical to use B2H6 diborane gas to diffuse boron into the silicon material. 向本征半导体中添加如硼、铝或镓这样的三价杂质，会形成价电子的缺乏，称为‘空穴’。通常使用B₂H₆二硼烷气体将硼扩散到硅材料中。

Bands for Doped Semiconductors

The application of band theory to n-type and p-type semiconductors shows that extra levels have been added by the impurities. In n-type material there are electron energy levels near the top of the band gap so that they can be easily excited into the conduction band. In p-type material, extra holes in the band gap allow excitation of valence band electrons, leaving mobile holes in the valence band.