[SI-LIST] Re: Subject: A Question on Electrons and Holes mobility
- From: "Stefan Milnor" <stefan.milnor@xxxxxxxxxxxxxx>
- To: <lgreen22@xxxxxxxxxxxxxx>, "Yagya Dutt Mishra" <ygdutt86.2@xxxxxxxxx>
- Date: Wed, 20 Jun 2012 16:42:27 -0700
Were there holes in his summary?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Lynne D. Green
Sent: Wednesday, June 20, 2012 4:39 PM
To: Yagya Dutt Mishra
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Subject: A Question on Electrons and Holes mobility
To resummarize your summary:
1) Yes for ideal semiconductors. NOT true if semiconductor contains impurities
or dopants (i.e.
all real semiconductors).
2) Yes for ideal semiconductors. NOT true if semiconductor contains impurities
or dopants (i.e.
all real semiconductors).
3) Yes for silicon. NOT true in general - in some semiconductors, holes have
greater mobility.
Regards,
Lynne
On 6/19/2012 10:59 PM, Yagya Dutt Mishra wrote:
> Okay so after reading all the answers allow me to summarize the whole
> concept ...
>
> 1) In conduction band *( there are just electrons coming from valence
> band ) *
>
> 2) In valence band *[ there are holes ( which was created by the
> electrons present in the conduction band + Electrons which are tightly
> bounded with nucleus ]*
>
> So the speed of holes in the valence band entirely depends on the
> speed of electrons in the valence band ( which i have mentioned in the
> second point that , they are tightly bounded by inter-atomic forces )
> . So the holes won't move unless and until electrons break them out
> from the orbit(which is a slow process).While the electrons in
> conduction band have no obstacle to face.
>
> Hence /_"Holes are less mobile"_/
>
> P.S : And so according to the first two points , we can also
> generalize the concept of the effective mass of electrons and holes .
> Since Conduction Band is at higher Energy level ( so applying the
> equation E=m.c² , which says higher the energy , higher would be the
> effective mass
> ) so the electrons which are present in the conduction band would have
> higher effective mass than the holes that they have left behind in the
> valence band..
>
> P.P.S : Thanks to all of you :) . I got the answer now.
>
>
>
> On Wed, Jun 20, 2012 at 10:53 AM, Lynne D. Green
> <lgreen22@xxxxxxxxxxxxxx <mailto:lgreen22@xxxxxxxxxxxxxx>> wrote:
>
> "Holes" are like bubbles in water. Holes prefer
> to rise in energy until they reach the top
> of the
> valence band. For both bubbles and holes, they
> can be described in terms of effective mass and
> energy.
>
> The carriers (electrons in conduction band,
> holes
> in valence band, bubbles in water) act as "free"
> carriers. They do not simply "hop" from one
> atom
> (or water molecule) to the next. This has to do
> with quantum properties energy bands compared to
> discrete energy levels.
>
> Electrons move more easily than holes because of
> the quantum properties of the crystal lattice.
>
> - Lynne
>
> PS:
> - A Google search for "Semiconductor Physics"
> found several books.
> - Unusual fact: Sometimes, the electron energy
> diagram shows a region of negative mass
> (example:
> GaAs). This quantum effect results in tunneling
> between two regions of positive mass.
>
>
> "IBIS training when you need it, where you
> need it."
>
> Dr. Lynne Green
> Green Streak Programs (and retired EE prof)
> http://www.greenstreakprograms.com
> 425-788-0412 <tel:425-788-0412>
> lgreen22@xxxxxxxxxxxxxx
> <mailto:lgreen22@xxxxxxxxxxxxxx>
>
>
>
> On 6/19/2012 9:36 PM, Chaitanya Satuluri wrote:
> > Yes. There is no holes in the world.
> >
> > chaitanya
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>
> [mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>] On
> Behalf Of Tesla
> > Sent: Wednesday, June 20, 2012 8:04 AM
> > To: sen.velmurugan@xxxxxxxxxx
> <mailto:sen.velmurugan@xxxxxxxxxx>
> > Cc: si-list@xxxxxxxxxxxxx
> <mailto:si-list@xxxxxxxxxxxxx>
> > Subject: [SI-LIST] Re: Subject: A Question
> on Electrons and Holes mobility
> >
> > Are there really "holes" in this world. it
> is actually electrons in moving.
> >
> > Tesla.
> >
> >
> >
> >
> > At 2012-06-20 02:15:51,"Sen
> Velmurugan"<sen.velmurugan@xxxxxxxxxx
> <mailto:sen.velmurugan@xxxxxxxxxx>> wrote:
> >> I hope you agree that, An electron only
> travel to next atom not to
> >> subsequent atom. That is.... due to
> Potential difference impressed on
> >> the medium, a new electron is kicked in
> to an atom, then a older atom
> >> kicked out into next atom, so it is a
> chain reaction.
> >>
> >> Holes exist only in a semi conductor a
> tighter medium called semi conductor.
> >>
> >> As the term implies, lattice is an highly
> uniformly structured medium,
> >> where an electron has more room to move,
> that is not hindered by too
> >> many free electrons, like an highspeed
> free way.
> >>
> >> For all the above mediums, you need
> appropriate potential difference to
> >> make electron to take part in the
> conduction called current. No PD no
> >> conduction, so mobility is like viscosity
> and PD is like pressure.
> >>
> >> Now, You need to use Bhors Atom model,
> shell energy level to make more
> >> sense on the availability of electron for
> mobility for a given PD.
> >> Hope I gave more perspective than an answer.
> >> ~Sen
> >>
> >>
> >> Date: Mon, 18 Jun 2012 11:34:50 +0530
> Subject: [SI-LIST] A Question on
> >> Electrons and Holes mobility From: Yagya
> Dutt Mishra
> >> <ygdutt86.2@xxxxxxxxx
> <mailto:ygdutt86.2@xxxxxxxxx>> *Hello all
> :) * * * *A very small question
> >> ...??*
> >> * * *Electrons have higher mobility than
> holes.As of now i know these
> >> reasons .. * * * *1) Since effective mass
> of electrons are less than
> >> holes so electrons are more mobile as
> compared to holes.* * * *2)
> >> (During the conduction) Electrons are
> present in conduction band and
> >> holes are in valence band * *( because of
> the fact that electrons
> >> jumped in the conduction band crossing
> the energy barrier and
> >> generating a hole in the valence band).*
> *Since valence band is denser
> >> as compared to conduction band (because
> of the presence of more charge
> >> carriers) ,* *electrons can freely move
> while hole in the valence band
> >> will face lots of attraction and
> repulsion.* * * *Now these two reasons
> >> are well satisfying theoretically but
> practically (if there is any
> >> other explanation emphasizing more on the
> solid physics of electrons
> >> and
> >> holes) by which i can understand more on
> this mobility issue please
> >> tell
> >> me.* * * *P.S : I have also read one
> thing "Electrons can move freely
> >> in lattice as compared to holes" :(
> [still an unconvincing reason]* * *
> >> * * *Thanks and Regards *
> >>
> >>
>
>
>
>
>
>
> --
> Yagya Dutt Mishra
> B.Tech Final Year
> Electronics and Communication Engineering Indian Institute of
> Information technology Allahabad Contact No : 08882016638
>
> Impossible can become possible if you are awesome :)
>
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