半导体Semiconductor

绝对零度时价带全满、导带全空，半导体不导电；升温时少量电子获得热能跃迁到导带，在价带留下带正电的“空穴”，电子和空穴都能导电，因此电导率随温度升高而增大，与金属相反。硅的禁带宽度 1.12 eV，砷化镓 1.42 eV（直接带隙，可高效发光），碳化硅约 3.3 eV，氮化镓 3.4 eV（宽禁带，适合蓝光和功率器件）。

At absolute zero the valence band is full and the conduction band empty, so a semiconductor does not conduct; as it warms a few electrons gain enough energy to jump into the conduction band, leaving positive holes behind, and both electrons and holes carry current, so conductivity rises with temperature, the opposite of metals. Band gaps are 1.12 eV for silicon, 1.42 eV for gallium arsenide (a direct gap, so it emits light efficiently), about 3.3 eV for silicon carbide and 3.4 eV for gallium nitride (wide gaps suited to blue light and power devices).

1833 年法拉第发现硫化银电阻随温度升高而下降。1874 年布劳恩发现金属硫化物的整流效应。1931 年威尔逊用能带理论解释了半导体。1947 年贝尔实验室的巴丁、布拉顿和肖克利发明点接触晶体管，三人获 1956 年诺贝尔物理学奖。1958–1959 年基尔比和诺伊斯发明集成电路。1993 年中村修二等实现高亮度氮化镓蓝光 LED（2014 年诺贝尔物理学奖）。

In 1833 Faraday found that the resistance of silver sulfide falls as it warms. Braun discovered rectification in metal sulfides in 1874. Wilson explained semiconductors with band theory in 1931. In 1947 Bardeen, Brattain and Shockley at Bell Labs invented the point-contact transistor and shared the 1956 Nobel Prize in Physics. Kilby and Noyce invented the integrated circuit in 1958–59, and in 1993 Nakamura and others made bright gallium-nitride blue LEDs (Nobel Prize in Physics 2014).

单质半导体有 Si、Ge；化合物半导体有 III-V 族（GaAs、InP、GaN）、II-VI 族（CdTe、ZnSe）、IV-IV 族（SiC）和氧化物（ZnO、IGZO）；还有有机半导体和钙钛矿半导体。高纯硅（9N 以上）由改良西门子法生产，再用直拉法拉制单晶。半导体是集成电路、太阳能电池、LED、激光器和传感器的基础。

Elemental semiconductors are Si and Ge; compound semiconductors include III–V (GaAs, InP, GaN), II–VI (CdTe, ZnSe), IV–IV (SiC) and oxides (ZnO, IGZO), along with organic and perovskite semiconductors. Ultra-pure silicon (better than 9N) is made by the modified Siemens process and grown into single crystals by the Czochralski method. Semiconductors underpin integrated circuits, solar cells, LEDs, lasers and sensors.