If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
What you have is two schottky diodes (metal semiconductor junction) in antiseries. Each metal-semiconductor contact forms a diode, which can point in either direction depending on whether the work function of your contact is greater or smaller than that of the SiC. In either case, when sufficient bias is applied, one will enter reverse breakdown, and the other will then be forward biased and conducting current, and then able to emit light.
Given which side lights up, I think your diodes are forward biased with the semiconductor positive wrt the metal, which would mean metal has a lower work function than your SiC.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
That makes sense. I picked up the crystal at a rock shop a few years ago. It's the smallest one, but it was the most efficient at making light.
Another interesting thing, the wavelength gets longer as it gets warm. At room temp it's yellow, but after a few seconds when the temperature raises to about 500*F, it's orange. Maybe i'll spray some canned air or butane on it to cool it and see if it turns green.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
That makes sense, as most semiconductors have a bandgap that decreases with temperature. I wasn't able to find a definitive reference on SiC, but it has been measured in straight silicon:
I found one paper which vaguely mentioned a 0.03eV increase in the bandgap from room temp to 2K. It might be subscription locked for you, but here it is:
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
It's black as can be. Most of the light comes from the surface, but when power is applied so the "half' glows (not the circle), it looks like there is light coming from inside too. Somehow it becomes slightly translucent.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
IntraWinding wrote ...
Matski: Would Grenadier get better results with a pair of different metal contacts such that one has a higher and one a lower work function than SiC?
He could, because then he could make it so that both schottky contacts are forward biased at the same time. I'm not sure what metals would be good for that though.
Another approach is to make only one contact a diode contact. This is a problem faced in any semiconductor process, making so called "Ohmic Contacts" which behave like a resistor rather than a diode. Ordinarily a good approach is to heavily dope the contact site, but that's tricky unless you try to rig up something like Jeri's doping/oxidation oven. I think you might get good results by just making a firm contact over a large surface area.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.