[SI-LIST] Re: si-list Digest V5 #210
- From: steve weir <weirsi@xxxxxxxxxx>
- To: venkat@xxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 23 May 2005 12:03:26 -0700
Venkat, it's a simple RC relation. MOSFET's have a positive tempco of
resistivity.
Steve.
At 12:25 PM 5/23/2005 -0500, Satagopan, Venkat Raghavan \(UMR-Student\) wrote:
>I guess I am missing something about this thread.
>My understanding from few of the threads is that=20
>Increase temperature leads to more number of electrons in conduction =
>band
>Increased temperature leads to reduction in threshold voltage Vt of say =
>MOSFET.
>Reduction of Vt would increase the switching speed of the device making =
>it faster.
>=20
>So how would reducing the temperature to liquid nitrogen levels make the =
>device work two to three times faster.
>Kindly help me clear my confusion.
>Thanks
>Venkat
>=20
>
>________________________________
>
>From: si-list-bounce@xxxxxxxxxxxxx on behalf of Tom Dagostino
>Sent: Mon 5/16/2005 6:51 PM
>To: arpad.muranyi@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: si-list Digest V5 #210
>
>
>
> From the Handbook of Physics
>
>Semiconductors..."At absolute zero the ideal structure is an insulator. =
>At
>elevated temperatures, electrons can be thermally excited from the =
>valence
>band to the conduction band, giving intrinsic conductivity from equal =
>number
>of conduction electrons and holes....."
>
>Tom Dagostino
>Teraspeed Labs
>13610 SW Harness Lane
>Beaverton, OR 97008
>503-430-1065
>http://www.teraspeed.com
>tom@xxxxxxxxxxxxx
>
>Teraspeed Consulting Group LLC
>121 North River Drive
>Narragansett, RI 02882
>401-284-1827
>
>Teraspeed is the registered service mark of
>Teraspeed Consulting Group LLC
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Muranyi, Arpad
>Sent: Monday, May 16, 2005 4:02 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: si-list Digest V5 #210
>
>
>Thanks for the two responses to my question from Lynne, and Chris.
>
>Let me recap the thread, and restate my question, because I don't
>feel that it was completely answered yet.
>
>The thread started with the question on what happens with silicon
>semiconductor devices below -55 C. A response came back to say
>that at 77 K silicon will act as an insulator. Someone else
>responded that this was not the case. Then the previous writer
>corrected themselves saying that they were referring to pure
>silicon being an insulator at such low temperatures.
>
>This is when I asked my question. I may have read too much into
>the thread, but it seemed to imply that PURE silicon is an insulator
>at those low temperatures, but less of an insulator at higher
>temperatures, such as room temperature. This surprised me.
>
>I am certainly not an expert in this area, but I thought that PURE
>silicon was an insulator because the way its crystal structure is
>built. There are no free electrons in it. I don't see how temperature
>can effect its conductance, unless something drastic starts happening
>in the crystal structure. Chris' response to my question pretty
>much confirmed this, although I would be curious to hear more about
>what those mechanisms are which can do that.
>
>Lynne's response seems to apply to doped silicon. I agree the mobility
>of those carriers can be influenced by temperature a great deal, but
>again, I was curious about PURE silicon, since that's what my first
>response (question) was triggered by.
>
>So is my recollection correct that at normal room temperatures and
>thereabout, PURE silicon would still be a perfect insulator, or does
>it have to be cooled way down (say to 77 K) to become an insulator?
>
>Thanks,
>
>Arpad
>-----------------------------------------------------------------------
>-----Original Message-----
>From: lgreen [mailto:lgreen22@xxxxxxxxxxxxxx]=3D20
>Sent: Monday, May 16, 2005 3:28 PM
>To: Christopher.Jakubiec@xxxxxxxxxxxx; Muranyi, Arpad; =3D
>si-list@xxxxxxxxxxxxx
>Subject: RE: [SI-LIST] Re: si-list Digest V5 #210
>
>Hi, Arpad,
>
>Silicon bulk resistivity (and conductivity) is strongly temperature
>dependent. At room temperature, the resistivity is higher than metals, =
>=3D
>but
>too high to use it as a good insulator (hence the name semi-conductor).
>Resistivity is also very sensitive to impurities, with the usual =3D
>impurities
>leading to a slightly n-type material in silicon.
>
>At "low" doping (about 10-100x the impurity level), the resistivity =3D
>becomes
>both lower and less sensitive to temperature. It also becomes possible =
>=3D
>to
>predictably control the built-in junction potential.
>
>At very high temperatures, of course, the thermally generated carriers =
>=3D
>can
>dominate over the doping. But that is normally outside the operating =
>=3D
>range,
>unless you get a local high current density.
>
>- Lynne
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
>=3D
>On
>Behalf Of Christopher.Jakubiec@xxxxxxxxxxxx
>Sent: Monday, May 16, 2005 2:17 PM
>To: arpad.muranyi@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: si-list Digest V5 #210
>
>Arpad,
>
>I agree with your statement to an extent. Current flow in silicon is
>related to the amount of free carriers (either holes or electrons) that =
>=3D
>are
>available to participate. Free carriers can be induced both by means of
>impurity doping in the silicon, and electron/hole pairs can be thermally
>generated even in pure silicon (although not normally for a practical
>purpose).
>
>Regards,
>
>Chris
>Infineon Technologies
>=3D3D20
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Muranyi, Arpad
>Sent: Monday, May 16, 2005 2:15 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: si-list Digest V5 #210
>
>
>Jut to clarify things I would like to ask a question:
>
>My understanding was that pure silicon is not conductive, not even at =
>=3D
>room
>temperature(?). The doping is what freezes up some electrons to make it
>conductive. How does this relate to temperature?
>
>Thanks,
>
>Arpad
>-------------------------------------------------------------------------=
>=3D
>--
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>=3D3D3D On Behalf Of Daniel Chow
>Sent: Monday, May 16, 2005 10:44 AM
>To: John Zasio
>Cc: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: si-list Digest V5 #210
>
>My bad.
>
>My statement was true for pure silicon.
>
>Heavy doping significantly changes the properties of silicon.
>
>
>
>-----Original Message-----
>From: John Zasio [mailto:zasio@xxxxxxxxxxxxxxxxxxx]=3D3D3D3D20
>Sent: Monday, May 16, 2005 10:25 AM
>To: Daniel Chow
>Cc: si-list@xxxxxxxxxxxxx
>Subject: Re: [SI-LIST] Re: si-list Digest V5 #210
>
>Daniel,
>
>Silicon devices do work and work well at liquid nitrogen =3D3D3D
>temperatures.=3D3D3D3D20 CMOS devices will run at two to three times =3D
>faster than
>at room temperature.
>
>In the mid 80s ETA Systems shipped a CMOS Supercomputer cooled by liquid
>
>nitrogen. Although the product was not a commercial success, =3D
>the=3D3D3D3D20
>technology worked very well.
>
>John Zasio
>
>Daniel Chow wrote:
>
> >Jon,
> >
> >No silicon part will work at liquid nitrogen temperatures (77 Kelvin).
> >
> >Silicon is an insulator at that temperature. The charge carriers are
> >"frozen out" at low temperatures.
> >
> >Please refer to Chapter 8 of "Solid State Physics" by Charles Kittel
>for more details.
> >
> >Thanks!
>
> >Daniel Chow, Ph.D.
> >Sr. Product Engineer
> >ALTERA
> >Office: (408) 544-8100
> >Fax: (408) 544-7602
> >Email: dchow@xxxxxxxxxx=3D3D20
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at: =20
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>=20
>
>
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
