Zener Diode: germanium vs. silicon

  • Thread starter Thread starter Number2Pencil
  • Start date Start date
  • Tags Tags
    Diode Silicon
Click For Summary

Discussion Overview

The discussion revolves around identifying whether a Zener diode is made of silicon or germanium based on its characteristic curve, specifically in the context of a lab experiment using a Curve Tracing machine. Participants explore the differences in behavior between silicon and germanium Zener diodes, particularly in reverse bias conditions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the validity of determining the material of a Zener diode based solely on the curve tracer, suggesting that the question may be misleading or could involve distinguishing between different types of diodes.
  • Another participant proposes that the saturation current (Isat) might differ between silicon and germanium Zener diodes, particularly in the reverse bias region before reaching breakdown.
  • There is mention of difficulty in finding data sheets for germanium Zener diodes, with one participant noting that silicon Zeners have a wide range of Zener voltages.
  • A participant recalls that germanium diodes may exhibit higher reverse leakage currents compared to silicon, although they express uncertainty about the specifics.
  • One suggestion is to check the part number of the diode, as certain prefixes may indicate the material type, although this may not apply universally.
  • Another participant highlights the difference in bandgap energy between germanium and silicon, suggesting that this could correlate with the observed reverse leakage characteristics.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the identification of the diode material based on the curve tracer data. Multiple competing views are presented about the characteristics of silicon versus germanium Zener diodes, and no consensus is reached on the best approach to determine the diode type.

Contextual Notes

Participants note limitations in the lab setup, specifically that only reverse bias measurements can be taken, which may restrict the ability to fully analyze the diode characteristics. There is also an acknowledgment of the lack of readily available data for germanium Zener diodes.

Number2Pencil
Messages
204
Reaction score
1
I have to utilize a Curve Tracing machine on a 5V Zener Diode for a lab. The curve tracer shows voltage vs. current. The lab asks me to examine the curve and determine whether it is a Silicon or Germanium diode, but I'm wondering...what would be different about the graphs of the two types? Wont they both have a shoulder near -5V?

Oh yeah, I only get to do it reversed biased, as it doesn't show 4 quadrants worth of graphs. So I can't look at the shoulder for forward biased. Is there a trick or is the question a trick?
 
Engineering news on Phys.org
This is a strange one, and I'm afraid I cannot help much. However, are you sure you're supposed to determine whether a *zener* diode is made of silicon or germanium? (If it's just a diode, we can inspect the forward threshold voltage, but I'm not sure about zener diodes. Could it be a question asking you to distinguish between a zener diode and an avalanche diode?)

What I'd do is look up data sheets on the two types of zener diodes beforehand and ascertain the differences in the region of interest on the characteristic curve, then do the lab work.
 
Maybe the Isat value is different between them? That's the reverse leakage current in the reverse bias region before you reach the Zener breakdown region. I don't know whether the Isat values will be different, but it's worth looking into.
 
I looked for a good while and couldn't find any data sheet online that specified a germanium zener diode. I did look at several Silicon zeners and found zener voltages ranging from 3V to 100V.

I guess I can't throw Silicon out just yet. And yes, I've double checked and it does ask to determine if the *zener* is silicon or Germanium
 
Don't know if this will help but there is a reference
http://prola.aps.org/abstract/PR/v83/i3/p650_1
 
Doesn't Ge has high reverse leakage compared to Si? (Or is my memory too hazy?) I think the difference is a very large factor (10's of uA/cm^2 vs 0.1 nA/cm^2), but maybe soemone can check in a book like, e.g., Sze.
 
Marcus, I think you hit it. I had forgotten about this and was reluctant to post since I couldn't think of anything other than to test it forward biased.
 
EDIT:yea you are right Supernova. my bad. Sorry I don't have an answer for the thread starter.
 
Last edited:
Read the first post again poo. He's only allowed to do it in reverse.
 
  • #10
Number2Pencil, can you share your results with us?
 
  • #11
The cheapskate way is forget about the curve tracer and read the part number. BZ... is a silicon zener, AZ... would be germanium, if such a thing exists.
 
  • #12
hmmm...wouldn't the fact that the Ge bandgap is smaller than Si's (higher valence shell) indicate that, as marcusl stated, the reverse leakage would be higher?
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K