Talk:Ohmic contact

Untitled
What this article still needs: some simple band diagrams illustrating the various energies; a table listing important metal-semiconductor contact combinations; a discussion of contact formation by implantation and annealing; a few words about barrier layers and electromigration. Alison Chaiken 00:57, 17 January 2006 (UTC)

Are the band diagrams for the ohmic contacts correct? I was under the impression that they should be reversed. In both cases, it appears that the majority carriers would have a difficult time moving from the semiconductor to the metal under zero (or negative) bias

Also, The Seebeck effect is not caused by ohmic or blocking contact. Rather, it is the flow of carriers due to a temperature gradient. This effect can happen in, say, a semiconductor by itself without any metal contact!

Needs new figure
Previous band diagram figure (now deleted) was obviously wrong, caption equated Schottky contacts with ohmic contacts. —Preceding unsigned comment added by 199.46.200.231 (talk) 19:15, 29 October 2009 (UTC)

band-bending
"The built-in field is the cause of band-bending in the semiconductor near the junction. "

But what is the reason of this? LMB 15:50, 18 September 2007 (UTC)

The field acts like a repulsion force - either negative repelling electrons or positive repelling holes. So this repulsion force effectively acts as a potential barrier, which is shown schematically as "band-bending" - because you have to (if you were an electron) travel up the hill to the metal side, or as a hole (imagine it being like a helium balloon) travel down the slope to the other side. 24.150.80.14 (talk) 03:19, 9 March 2009 (UTC)

semiconductor depletion region?
Umm... wouldn't a depletion region make it a Schottky barrier instead? Tunneling through a depletion region is called punch through, and it's a diode breakdown mechanism (see zener diode), but that contradicts the article's definition of an ohmic contact has having linear I-V.

Also Streetman says "Unlike the rectifying contacts discussed previously, no depletion region occurs in the semiconductor in these cases sinc ethe electrostatic potential difference required to align the Fermi levels at equilibrium calls for accumulation of the majority carriers in the semiconductor."

So I was just coming here to look for an equation to find the width of the accumulation region and there's this about depletion... this isn't my specialty but unless someone wants to defend this I think much of the main section will get ripped out.

I don't see how the penetration of the effects of the metal would depend on preexisting carrier density here. Potatoswatter 23:03, 7 November 2007 (UTC)

there is anorther contact called the rectifying contact... —Preceding unsigned comment added by 117.194.67.5 (talk) 15:44, 26 February 2009 (UTC)

Clarification needed?
I suspect "the difference between the Fermi energy and the vacuum level" needs clarification, e.g., specifying an electron. Even then, I would think you would need to day still more. —Preceding unsigned comment added by Pvkeller (talk • contribs) 16:40, 1 November 2009 (UTC)

Energy Barrier?
"In a classical physics picture, in order to surmount the barrier, a carrier in the semiconductor must gain enough energy to jump from the Fermi level to the top of the bent conduction band. The needed barrier-surmounting energy φB is the sum of the built-in potential and the offset between the Fermi level and the conduction band."

The fermi level in the semiconductor is the the band gap so how can there be carriers there? I guess in a classical picture there wouldn't be energy levels that weren't allowed. Even so perhaps it's not so good to be describing quantum phenomena classically —Preceding unsigned comment added by 137.222.44.207 (talk) 12:18, 5 October 2010 (UTC)

Best metals for ohmics
The article says:
 * The simple theory presented above predicts that $$\phi_B = \phi_M - \chi_S$$, so naively metals whose work functions are close to the semiconductor's electron affinity should most easily form ohmic contacts. In fact, metals with high work functions form the best contacts to p-type semiconductors while those with low work functions form the best contacts to n-type semiconductors.

The first sentence doesn't make any sense at all. I think it is pretty obvious from the simple model (called Schottky-Mott rule by the way) that the higher the work function of the metal, the more the band bends down and the better the contact will be to n-type. It will basically induce locally an n+ region near the interface, and the more n+ it is the better. And the opposite holds as well, that the lower the work function of the metal, the more the band bends up and the better it is for p-type. Why should exactly matching the work function and electron affinity help? There is no optimum there.

(on a side note, it would be nice if the contact materials table at the bottom were sorted into n-type contact materials and p-type contact materials) --Nanite (talk) 17:35, 9 June 2013 (UTC)

Surface-cleaning etchants
I don't think bromine-methanol is the most-used surface-baring treatment on GaAs before metallization. That sounds like carry-over info from early times. Device-makers I have worked at always used dilute HCl as the last step, just to strip away the thin native oxide of GaAs. It had the advantage of leaving no carbon-bearing contamination on the bare surface. jimswen (talk) 22:42, 12 February 2023 (UTC)