掺杂Doping (semiconductor)

硅有 4 个价电子。掺入第 15 族的磷、砷，杂质原子用 4 个电子与周围硅成键后多出 1 个电子，它束缚很弱（约 0.045 eV），室温下几乎全部电离进入导带，形成 n 型硅，多数载流子是电子。掺入第 13 族的硼，缺 1 个电子形成空穴，受主能级约在价带上方 0.045 eV，形成 p 型硅，多数载流子是空穴。百万分之一的掺杂就能使硅的电导率提高上万倍。

Silicon has four valence electrons. A group 15 dopant such as phosphorus or arsenic uses four electrons to bond with neighbouring silicon and has one left over, bound so weakly (about 0.045 eV) that at room temperature nearly all are ionised into the conduction band, giving n-type silicon with electrons as majority carriers. A group 13 dopant such as boron is one electron short and creates a hole, with an acceptor level about 0.045 eV above the valence band, giving p-type silicon with holes as majority carriers. Doping at one part per million can raise silicon's conductivity by a factor of ten thousand or more.

1940 年贝尔实验室的奥尔发现硅样品中天然形成的 p-n 结在光照下产生电压，并认识到杂质类型的区别。早期采用高温扩散法掺杂，1950 年代起发展了离子注入技术，可精确控制杂质深度和剂量，成为现代集成电路制造的标准工艺。化合物半导体中掺杂更复杂，例如 GaN 的 p 型掺杂（镁）直到 1989 年天野浩和赤崎勇用电子束退火激活才实现，这是蓝光 LED 的关键突破。

In 1940 Russell Ohl at Bell Labs found that a silicon sample with a naturally formed p–n junction produced a voltage in light, and recognised the different impurity types. Early doping used high-temperature diffusion; ion implantation, developed from the 1950s, controls depth and dose precisely and became standard in chip manufacture. Doping compound semiconductors is harder: p-type GaN (with magnesium) was achieved only in 1989, when Amano and Akasaki activated it by electron-beam annealing, a key step toward blue LEDs.

“掺杂”一词也用于其他材料：导电高分子的氧化还原掺杂、荧光粉中稀土离子掺杂（如 YAG:Ce³⁺ 白光 LED）、激光晶体（Nd:YAG）、超导体中的载流子掺杂（如 La₂₋ₓSrₓCuO₄），以及固体电解质中的异价掺杂产生空位。

The word doping is also used for other materials: redox doping of conducting polymers, rare-earth doping of phosphors (YAG:Ce³⁺ in white LEDs), laser crystals (Nd:YAG), carrier doping of superconductors (La₂₋ₓSrₓCuO₄) and aliovalent doping of solid electrolytes to create vacancies.