Can Diodes Become Nonlinear and Cause Device Failure at Reverse Breakdown?

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Discussion Overview

The discussion revolves around the nonlinearity of diodes, particularly focusing on their behavior under forward and reverse bias conditions, and the implications of reverse breakdown on device failure. Participants explore the underlying mechanisms of current flow in diodes, including the exponential characteristics observed in their I-V curves.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants explain that diodes are nonlinear due to their polar nature, which allows current to flow in one direction while restricting it in the reverse direction.
  • There is a question regarding the regions of exponential change in both forward and reverse bias, with one participant noting that reverse breakdown leads to a significant increase in current once a certain voltage is reached.
  • Another participant discusses the intrinsic potentials of the p and n regions, stating that a forward bias narrows the energy gap, allowing current to flow once a threshold voltage (approximately 0.6 to 0.7V for silicon) is achieved.
  • One participant mentions that at reverse breakdown, the material may melt and develop shorts, leading to device failure.

Areas of Agreement / Disagreement

Participants express varying levels of understanding about the mechanisms behind diode behavior, with some agreeing on the basic principles of biasing and exponential current flow, while others raise questions that indicate uncertainty and a lack of consensus on specific details.

Contextual Notes

There are unresolved questions regarding the precise nature of current flow in both forward and reverse bias conditions, as well as the implications of reverse breakdown on diode integrity. The discussion reflects a range of assumptions about the behavior of charge carriers and the conditions under which diodes operate.

Who May Find This Useful

This discussion may be useful for students and professionals interested in semiconductor physics, electronic engineering, and the operational characteristics of diodes in various applications.

impendingChaos
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Why are diodes nonlinear?
 
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They have a polar nature to them because biasing them one way helps the current to flow, but biasing them the other way (reverse bias) forms a boundary to charge flow, so very little current flows when the diode is in reverse bias.

Here's a wikipedia page in case it helps: http://en.wikipedia.org/wiki/Diode
 
I understand the concept of the biasing but why do you have these regions of exponential change in the reverse and forward biased directions. From what I have read,when the diode is reverse biased the current which it trying to pass through it is exciting the electrons but the potential drop is too much to overcome for a time (besides the small leakage current). However, once the reverse breakdown voltage is achieved the excited electrons rush out in an exponential inverse voltage. But why is this exponential region apparent in the forward biased direction since the diode is meant to allow current to flow in that direction. For example why must silicon reach a voltage on .65 V before the current takes off so to speak? Does the diode inhibit current in the forward biased direction as well?
 
I misspoke when I said the "current" is exciting the electrons, the current is electrons. duh
 
The p and n regions are at different intrinsic potentials, with an energy (voltage) gap preventing current flow. The charge carriers can't flow "uphill." When you apply a reverse bias, the gap gets bigger and again no current flows (except for a little leakage). When you apply a forward bias voltage, it narrows the gap. At room temperature in Silicon, 0.6 to 0.7V sufficiently flattens the gap that carriers can flood across.

The exponential behavior comes from the thermal Boltzmann distribution of carrier energies. At room temperature some carriers have thermal (kinetic) energy, but energetic ones are exponentially less numerous than slow or stationary ones. Carriers with more energy than the gap can flow across (jump the hill), carrying a current. As you increase the forward bias voltage, exponentially more carriers have enough energy. That's why the I-V curve is exponential.
 
BTW, at reverse breakdown the material typically melts and develops shorts, and usually the device needs to be thrown out.
 

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