Why we use metal contact in PN diode at surface(both end)? We can have directly passed the current without using it.

Is it due to surface recombination velocity? If so then How.

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    \$\begingroup\$ How do you want to connect the diode to the rest of a circuit? \$\endgroup\$ – horta Aug 23 '17 at 18:16
  • \$\begingroup\$ Just a battery is connected to diode in forward or reverse bias. \$\endgroup\$ – ironman Aug 23 '17 at 18:19
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    \$\begingroup\$ Connected how? \$\endgroup\$ – Eugene Sh. Aug 23 '17 at 18:21
  • \$\begingroup\$ It is not connected anywhere in the circuit. I just want to know the behavior of diode near the metal contact at end side of diode. \$\endgroup\$ – ironman Aug 23 '17 at 18:27
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    \$\begingroup\$ You need to edit your question to greatly clarify what you want because as it stands, we're all trying to figure out what you're even asking. \$\endgroup\$ – horta Aug 23 '17 at 18:30

If you don't use a metal contact fabricated directly to the PN junction, an oxide or other surface contaminant will likely prevent you from making good contact with the diode. Fabricating the metal contacts directly onto it and then providing you with leads allows you to easily connect the PN junction to the rest of the circuit.

In the old days, they did make diodes out of point contacts where a semiconductor was just touched with a metal probe to make a schottkey diode.

Near the metal contacts, they usually increase the dopants greatly to enable an ohmic contact to occur between the semiconductor and the metal contact. This increase in dopants greatly increases the conductivity of the semiconductor basically turning it into something as conductive as metal itself.

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  • \$\begingroup\$ I want a mathematical approach and explanation \$\endgroup\$ – ironman Aug 23 '17 at 18:28
  • \$\begingroup\$ Mathematical approach to what? To the fact that the doped silicon is not soldering well? \$\endgroup\$ – Eugene Sh. Aug 23 '17 at 18:38
  • \$\begingroup\$ @pintuiitbhi Eugene's question stands. A mathematical approach to what? \$\endgroup\$ – horta Aug 23 '17 at 18:41
  • \$\begingroup\$ @horta During my class lecture professor used boundary condition in P doped side to find the equation of minority charge carrier as a function of position. And he used number of minority charge carrier at metal contact zero and at junction high conc. But How this thing happened? \$\endgroup\$ – ironman Aug 23 '17 at 18:47
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    \$\begingroup\$ @pintuiitbhi I think you need to show what notes you have or simply ask him. All of this should have gone into your question. \$\endgroup\$ – horta Aug 23 '17 at 19:13

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