How do electrons and holes move?

Electrons and Holes

"Conduction current" meaning current due to flow of electrons in "conduction band".

Re: Electrons and Holes

i too would like to call it something like that but the greyheads have already classified and named different currents before we were even born so we cant call them so unless someone has made "conduction current" as the standard name for that current...

Re: Electrons and Holes

this discussion is good though it's elementary. it refreshes. could you explain velocity ratio between electrons and holes in ICs?

Re: Electrons and Holes

forkschgrad said:

this discussion is good though it's elementary. it refreshes. could you explain velocity ratio between electrons and holes in ICs?

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________________2 /
Electron mobility, cm / volt sec
_____________2 /
Hole mobility, cm/ volt sec

(Both are Temp. dependant)

(Temp of Si = 290 K or 522 F)
Electron drift velocity(Si) is greater than hole drift velocity(Si) by 2.82 to 1
(see note 1 below). I know this is "elementry" for you,forkschgrad, But, why
don't you give us the theoretical explaination as to the reason for electron
velocity being greater than holes.
Please feel free to go into detail.

SpectraBEI

Note 1: The drift velocity of electrons and holes should not be constrained by a simple ratio. Temperature, Impurities, Electric Fields and other things (that I'll let forkschgrad go into in his upcoming thesis) have there effects on drift velocity. To put drift velocity in ratio form is (from my standpoint) unwise.

Re: Electrons and Holes

I disagree with this statement. It is absolutely predictable, and controllable, it is called "current flow".

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dear Spectrabei,

If you have read my comment closely it says "INSTANTANEOUS". What you are talking is (if understood right..!) is the "NET" flow of elec/hole current. Please read any basic electronics book and you shall surely agree with me...!!

Sai

Re: Electrons and Holes

raghuram_msc said:

I disagree with this statement. It is absolutely predictable, and controllable, it is called "current flow".

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dear Spectrabei,

If you have read my comment closely it says "INSTANTANEOUS". What you are talking is (if understood right..!) is the "NET" flow of elec/hole current. Please read any basic electronics book and you shall surely agree with me...!!

Sai

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Instantaneous = occuring or present at a particular instant.
Basic Electronics? LOL ! If all IC manufacturers believed as you do we would still be tinkering with leaky germanium transistors.
This is a science my friend, nothing is left undone or unknown.

SpectraBEI

Re: Electrons and Holes

Dear Spectrabei,

The current wave in any conductor propagates because of the mutual exchange of energy between charge carriers. These include collisions- both elastic and inelastic. During this the charge carriers tend to 'move' in rather statistical/random manner. In absence of external biases these collisions result in net zero current. That is why we cannot measure any voltage across an unbiased conductor with a multimeter because it reads only RMS values, which in this case is zero.

In biased condition also the manner in which current wave propagates is still statistical because of these random collisions, but, now there is a "net flow" superimposed on charge carriers in the direction of bias.

This is what i meant precisely..!!! If only you had read some book you would have known this.

LOL ! If all IC manufacturers believed as you do we would still be tinkering with leaky germainium transistors.

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And would Mr. Spectrabei be kind enough to explain from where the "leaky" germanium transistor has materialised from??? Or is this man's brain rather full(and therefore "leaking"..!!!) because

This is a science my friend, nothing is left undone or unknown.

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there is nothing left hiden from our friends wisdom...!!!!

Thinking ourself clever is confidence....
Thinking ourself alone clever is overconfidence.

I greatly pity people who post only to gain few points......

Sai

Re: Electrons and Holes

This is raghuram_msc latest post:

raghuram_msc said:

Dear Spectrabei,

The current wave in any conductor propagates because of the mutual exchange of energy between charge carriers. These include collisions- both elastic and inelastic. During this the charge carriers tend to 'move' in rather statistical/random manner. In absence of external biases these collisions result in net zero current. That is why we cannot measure any voltage across an unbiased conductor with a multimeter because it reads only RMS values, which in this case is zero.

In biased condition also the manner in which current wave propagates is still statistical because of these random collisions, but, now there is a "net flow" superimposed on charge carriers in the direction of bias.

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This is raghuram_msc ORIGINAL POST:

raghuram_msc said:

Dear All,

The discussion has been very interesting.

I quite agree with Mr. Cool, that electrons barely move on few cm (mind you not even meters...!!!! , Ref:- chap-1 M.E. Vanvalkenburg, "N/W analysis", PHI) in practise. So what we r talking is electron (or hole) "current" and not their physical movement..!! Yes, it is this electron (or Hole) current that propagates with the speed of light..!!

The concept of electrons (or holes) in energy band(s) is to convey only their relative energy levels and NOT THEIR PHYSICAL POSITION INSIDE THE ATOM..!! The idea of external biasing is to readjust these levels accordingly, remeber "forward" and "Reverse" biases??

The excitation of charge particles (Holes/Electrons) and their instantaneous movement across the conductor (or semiconductor) is a statistical affair and therefore not predictable accurately. that is why we could only specify RMS values.

Hope this is correct, Let me know if Iam wrong..!!

Sai

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In raghuram_msc original post he states the following "The EXCITATION of charge particles (Holes/Electrons) and their instantaneous movement across the conductor (or semiconductor) is a statistical affair and therefore not predictable accurately".

EXCITATION means STIMULATION in order to have STIMULATION there needs to be an EXTERNAL STIMULI. This means that (according to your original post) THERE IS "EXTERNAL BIAS" applied to the conductor. In the case of a wire it would be voltage. In (SI) it would be voltage, light, heat etc. Ya Know I Don't see the words "In absence of external biases" in your original post. I see it in your last post. Must be because you hit that BASIC ELECTONICS book that you keep talking about.
It's interesting to note that "raghuram_msc" has changed the verbage in his most recent post. He's trying to slyly change what he said in his original post. To cover his lack of knowledge. Take a look at his latest post (first quoted post)and then compare it with his original post (second quoted post).
The Differences Are Obvious...

OH, BY THE WAY, YOUR ORIGINAL POST IS, WRONG


And if you don't know what Germanium is, or the nature of its properties, then were not having this conversation.

Spectrabei

Re: Electrons and Holes

the instantaneous momentum and position of the electron cannot be determined exactly... there is a uncertainity related to it given by heisenberg's uncertainity principle....
just wanted to add on what i know

Re: Electrons and Holes

wow what a great discussion on an age old debate. I remember my first run-in with it in the version "which direction does electricity flow, + to - or - to +. Not until I learned years later about electrons then holes did I really grasp the concept. And although familiar with the physics of semiconductors and such, I did not know such detail. Great to have new ammo to baffle opponents if/when I happen upon this debate again.

I know that anti-matter is no longer the realm of science fiction so the following is stated "tongue-in-cheek" and not meant to insult real science.

Once upon a time the hole thing did not matter because only the electrons are matter, but along came Star Trek with it's anti-matter and changed the hole electron issue into a debate of hole-y anti-matter vs anti-hole matter. I just wanna know if gravity matters or anti-matters when debating the hole matter about the direction of the flow. PS - Did you know Capt Kirk invented anti-matter? According to him he's the only thing that matters so all else must be anti-matter. (Again just a joke based on the image he has created in recent years)

Electrons and Holes

^^^^ All ppl frm texas crack such jokes ??

Re: Electrons and Holes

know this is "elementry" for you,forkschgrad, But, why
don't you give us the theoretical explaination as to the reason for electron
velocity being greater than holes.
Please feel free to go into detail.

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excuse me,

the topic about electrons/holes is basic because it's the foundation. if you want to know the above elementary side, we are already dealing with its applications and in-depth details. Maybe, on an engineer's opinion it's a basic one but for a physicist it's a complicated one. it's me who ask the details why are you asking me? what do you want to prove? that you're the genius here?

i'm not.