non_equil

# non_equil - Current Flow in PN Diodes S Tewksbury The...

This preview shows pages 1–5. Sign up to view the full content.

Current Flow in PN Diodes S. Tewksbury The conditions leading to the flow of current in a PN diode under forward bias are rather complex. These slides have been developed to help you “see” the underlying things that are happening. I recommend that you go through the material carefully, keeping track of the sequence of steps along the way. If you can understand the concepts that lead to the actual way a PN diode works, you will be far more able to visualize other kinds of devices. I have tried to show systematically how the math is applied as we proceed through the various steps. I recommend that you spend some time understanding the math that is used. It is not difficult, simply easy to get lost in.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
P-Type semiconductor: N a N-Type semiconductor: N d E C E V E F E i E i - E F E F - E V E C E V E F E i E F - E i E C - E F The majority carrier density is n n = n i exp E F E i kT = N d , the donor density. From this we obtain E F E i , namely E F E i = kT ln N d n i The minority carrier density is given by p n = n i exp E i E F kT The majority carrier density is p p = n i exp E i E F kT = N a , the donor density. From this we obtain E i E F , namely E i E F = kT ln N a n i The minority carrier density is given by n p = n i exp E F E i kT
P-Type semiconductor N-Type semiconductor Depletion Layer p p ,0 = n i exp E i E F kT = N a E i E F P side = kT ln N a n i Equations for carrier concentrations n n ,0 = n i exp E F E i kT = N d E F E i N side = kT ln N d n i Equations for carrier concentrations 0 volts 0 volts n p,o p p,o p n,o n n,o E V E F E C E C E V E F E F - E i E i - E F E i E i Δ E i = E i E F ( ) P side + E F E i ( ) N side [ ] Total energy drop across depletion layer

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
P-Type semiconductor N-Type semiconductor Depletion Layer p p ,0 = n i exp E i E F kT = N a E i E F P side = kT ln N a n i Equations for carrier concentrations n n ,0 = n i exp E F E i kT = N d E F E i N side = kT ln N d n i Equations for carrier concentrations 0 volts 0 volts Δ E i = E i E F ( ) P side + E F E i ( ) N side [ ] = kT ln N a n i + kT ln N d n i = kT ln N a N d n i ( ) 2 E = qV relates energy to voltage. The built - in voltage is therefore V bi = kT q ln N a N d n i ( ) 2 .
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern