Forward Voltage: LEDs and Rectifier Diodes

[Diggsworth]

Why do LEDs have a higher forward voltage than rectifier diodes?
From what I understand, it has something to do with their chemical make-up, but I'm pretty sure there's more to it than that, anyone know the specifics?

 

[MikeMl]

Read the Wiki.

 

[Diggsworth]

I've already read through the bulk of the post.
I haven't been able to discern from it exactly why the forward voltage on LEDs is higher than rectifier diodes, though.

 

[MikeMl]

Ok, then see if this helps.

 

[Diggsworth]

Okay, then.
So it's because of the GaAs compound then, right?
Because the breakdown voltage, and therefore knee voltage of GaAs components are themselves higher than Si devices?
And this would be the 1.7V on LEDs vs. the 0.7V on rectifier diodes, right?

 

[MikeMl]

My recollection is that it has to do with the Physics: Band Gaps, impurities, doping concentrations, junction profile, diffusion depths, the phase of the moon, etc.

 

[Diggsworth]

Thanks, Mike.

 

[KeepItSimpleStupid]

The forward voltage for Germanium, I believe is about 0.2 V.