Are there any, between the 0.6-0.7V of a regular diode and the (at least) 2V of an LED? Yes, I know that you can chain diodes.

Play with forward current and Temperature of a power diode according to Schokley equation..

Quote from: antonis on October 25, 2024, 05:18:49 PMPlay with forward current and Temperature of a power diode according to Schokley equation..

That sounds stressful 

Quote from: fryingpan on October 25, 2024, 05:06:14 PMAre there any, between the 0.6-0.7V of a regular diode and the (at least) 2V of an LED? Yes, I know that you can chain diodes.

10 times the current will only get you 60mV to 120mV anyway.

In between cases are usually done with a VBE multiplier.   The down side here is it's not an ideal diode but more a diode with a parallel and series resistance;  lower series resistance traded for lower parallel resistance.

IR and deep red "non-hyper-output" LEDs run 1.1 to 1.2V forward.

Clip at 0.7V, amplify by 1.4X, same as a 1.0V clip.

Of course, there are workarounds. My semiconductor studies are rather rusty, but I seem to remember that it all depends on dopant concentrations (but I presume you eventually settle on a certain range for conductivity) and semiconductor chemistry, with GaAs and other formulations achieving higher forward voltages.

Here's a great capsule explanation of the turn on voltage:
Physics Stack Exchange

It is a a variable depending on dopant levels and junction geometry on top of the electron shell structure of the elements involved, and - yikes! The nominal forward voltage happens to be a good-enough approximation of what happens so we can bang out a design, then refine it.

Quote from: fryingpan on October 26, 2024, 04:11:33 AMOf course, there are workarounds. My semiconductor studies are rather rusty, but I seem to remember that it all depends on dopant concentrations (but I presume you eventually settle on a certain range for conductivity) and semiconductor chemistry, with GaAs and other formulations achieving higher forward voltages.

The turn-on voltage closely related to the Band-gap voltage of the material used.

You can see I0 in equation 1, but in equation 3 you can see the I0 depends on the band-gap voltage.
https://physics.csuchico.edu/~eayars/publications/bandgap.pdf
(The equations in the paper present Eg as an energy but you can present it as a voltage Vg.)

That means the ideal diode equation always has a term like exp( (Vd - Vg)/Vt ) where Vd=diode voltage, Vg is the band-gap voltage and Vt = thermal voltage (26mV @ 300K).  (See Rg's link for the Vg/2 form).

The thing is you can't change the band-gap voltage since it's determined by the material.   LEDs are an example where the band-gap can be manipulated but the same tricks aren't used for normal parts.    In fact the color of the LED is related to the Bandgap voltage; higher voltage = shorter wavelengths.