reverse breakdown voltage

Bernhard Kuemel · 2012-04-25T17:49:31+00:00

Hi seb!I tried to measure the Vrbd of LEDs and found the resistance dropping:Vr R(MOhm)3.18 244.61538461543.97 59.25373134334.23 48.62068965524.82 36.79389312985.65 27.56097560986.08 22.77153558057.61 16.295503212I guess I have not reached the breakdown voltage and I need a powersupply with more voltage.However, I wonder, what the definition of breakdown voltage is. Usuallyyou see the sharp increase in current at Vbd in the diode characteristiccurve. But isn't this a matter of zoom? When I use nA instead of mA onthe current axis the curve will look similar with the breakdown(forward) voltage shifted towards 0. IMHO the curve will look exactlythe same if it's a purely exponential curve and you zoom in or out.Or is there a voltage below which no impact ionization occurs and thiscan be seen as lowest possible definition of Vbd? But I rather thinkthere is always a chance for a free electron to gain enough energy toknock free another electron. It'll just never make an avalance throughthe whole barrier below a certain voltage. OTOH if a single electrontravels through the barrier due to a low voltage and at the other sideit happens to get bounced around by the lattice atoms to enough energyto kick free a second electron that's an avalanche that made it throughthe whole barrier. So at any voltage there'll be avalanches andavalanche current will increase (exponentially, I guess) over the wholevoltage range.Then there's zener breakdown which I think is some kind of tunneling.Bernhard

Apr 25, 2012 20 Replies

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Phil Hobbs 14 years ago

dropping:

power

Usually

characteristic

mA on

exactly

out.

and this

think

energy to

through

electron

other side

energy

through

the whole

tunneling.

concentrated on

Try

an idea.

incandescent

that LED.

just the

and

photo

using the

quoted text -

Now _that_ is cool. It really does look like a single-photon process, albeit inefficient.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net

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