Question

Are zener effect and quantum tunneling any way related to high voltage sparks or lightning ?

Answer 1

I think Zener affect fail at high voltage (not sure though)

Answer 2

Yes, in semiconductors, at higher voltages, avalanche effect occurs before the zener effect.

Once the avalance effect starts, huge current starts flowing in the semiconductor device and zener effect stays silent.

Answer 3

Zener effects and quantum tunneling in semiconductors usually occur in PN diodes as a result of DC reverse biasing so that the bandstructure is thin enough at a point to create tunneling. Now, if the voltage spark is high enough, that diode can at a moment operate at Zener breakdown. But I don't think this usually happens, since usually for most PN diodes there is a delay in regards to biasing (i.e., switching from forward to reverse) as a result of different factors. The only way I could imagine tunneling occurs as a result of high voltage sparks is found in MOSFETs as a result of damage to the oxide layer, but that's a different mechanism from Zener breakdown.

Answer 4

Ahh nice, velocity saturation in a MOSFET is due to quantum tunneling is it ?

Both, sparks that we see with out naked eye and the zener breakdown that we cannot see involve ionizing the atoms. Both events require the electric field to reach 300,000 V/m. I came across these two concepts at different places and wondering if these are same things...

Answer 5

well not quite; velocity saturation in MOSFETs are more due to scattering mechanism on a nanoscale that leads to velocity saturation.

I think I have a better picture of what you're asking though. I suppose you can say in the classical sense both mechanisms occur due to ionization (in that electrons get ripped from atoms), but to get a better picture you should really describe zener breakdown as quantum mechanical in nature. In a high voltage spark, the electrons as a result of scattering in the classical sense deviates from the normal conductive pathway (a resistive element for example) and excite the air it interacts with. In general, these sparks behave classically and are meant to reduce the potential between the two points.

Zener breakdown and QT in general are NOT classical behaviors. In the classical regime, Zener breakdown should not happen, as the high voltage and energy bandgap in semiconductors will impede the electrons from moving away from a semiconductor structure like a PN Diode (where in the reverse bias case they want to move away as a result of diffusion). But because electrons are wavelike in nature, they have a finite probability of moving through the barrier created by voltage and bandgap to create a finite breakdown current. This usually causes defects in the semiconductor and leads to the irreversible damage you find in normal PN diodes.

Answer 6

That's a very clear explanation, thank you @dominusscholae

Basicaly quantum tunneling is the reason for zener breakdown at high electric fields in a thin region. Sparks that we see are due to electron scattering and the released electrons are no longer confined, so we don't need quantum tunneling to explain this behavior. But we do need quantum tunneling to explain how the electrons are released from the confined surface right ?

Answer 7

Correct