why si is widely used than ge?

[sandy92]

silicon is mostly used in semiconductor applications than ge ,why?

 

[Mehtab Ali Zahid]

germanuim is unstable at high temperature because its valence electrons are in fourth shell, while silicon valence electrons are in third shell, so its stable at high temperature.

 

[Mehtab Ali Zahid]

silicon is cheaper as well, sandy

 

[Mikebits]

Silicon is the most common mineral on the planet.

 

[Ratchit]

Mehtab Ali Zahid,

germanuim is unstable at high temperature because its valence electrons are in fourth shell, while silicon valence electrons are in third shell, so its stable at high temperature.

Stable with respect to what?

silicon is cheaper as well, sandy .

Germanium is cheap enough already. Don't you think germanium would be in wide use if it was superior to silicon?

Mikebits,

Silicon is the most common mineral on the planet. .

Maybe so, but the expensive process used to convert it to ultrapure crystalline silicon negates any saving in availablity.

Ratch

 

[Sceadwian]

Ratchit, you know what happens to linearity of silicon devices as the heat is increased, Germanium circuits exhibit this effect dramatically more, but they have their uses as the voltage drop across a Germanium diode is about .15 volts as opposed to silicons .6, which makes them useful for certain things. It will probably be used quiet a bit more in the future only it will be a mix of SeGe, as the two together have superior properties than either one alone.

 

[RCinFLA]

The largest reason was creating an easy stable insulator layer. On silicon, just heat it and subject it to oxygen. Silicon grows insulating glass layer this way (SiO2). Ge has to have a separate vacuum deposition for insulating layer. A more expensive process.

 

[Sceadwian]

Probably why the SIGE alloys are becoming more widely used, just enough Ge to alter the semi conductor properties with the Si still being dominate for insulation.

 

[RCinFLA]

At the small geometries used today, most insulating layers are done by vapor deposition anyway which opens the door for use of SiGe which uses the higher mobility of Ge to yield better RF performance for the SiGe hybrid process. Many cellular RF chips are done in SiGe.

Silicon mobility = 1500 cm^2/V-s
Germanium mobility = 3800 cm^2/V-s
Gallium arsenide mobility = 8500 cm^2/V-s