n-type and p-type materials
A semiconductor material that has been subjected to the doping process is called an extrinsic material.
There are two extrinsic materials of immeasureable importance to semiconductor device fabrication: n-type and p-type materials.
n-Type Material
n-type就是有five valence electrons(pentavalent), 比如锑,砷,磷。这多出来的电子,不和共价键关联,成为一种相对free的状态。
Diffused impurities with five valence electrons are called donor atoms.
要注意的是,虽然n-type多了很多free carriers,但是始终是中性的。因为positively charged protons in the nuclei和free and orbiting charged electrons数量相等。
doping之后,在原来的energy level,又加了一层
p-Type Material
同理加入three valence electrons,比如硼,镓,铟。这样共价键就缺失了一个电子。
The diffused impurities with three valence electrons are called acceptor atoms.
和n-type一样,p-type也是中性。
Electron versus Hole Flow
当一些电子吸收了能量,打破共价键,填充到hole中,释放电子的地方就形成了hole。看起来像是电子的流动或者hole的流动。
Majority and Minority Carriers
一半的Ge和Si,只有少数的电子获得能量打破共价键,留下holes。n-type电子远比hole多,而p-type,hole远比电子多。其实主要是参杂的一方电子或hole急剧增多。
In an n-type material the electron is called the majority carrier and the hole the minority carrier.
In a p-type material the hole is the majority carrier and the electron is the minority carrier.
当donor atom的第五个电子离开parent atom,这个atom就带有正电
n-type和p-type是semiconductor devices的basic building blocks,比如把它们合并在一起,就会形成p-n结,是不是很酷😊