In the previous chapter, we saw how a symmetrical PN junction works. Let’s see what happens if the doping concentrations in the P and N regions are not the same.
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Imagine we magically connect P-type and N-type pieces of Si together. The doping concentration of the p-side is 5E13 per cm^3. You can choose the doping concentration of the N side.
Doping Concentration (per cm3):
After reaching equilibrium, compare the values of the charge density and electric field in the depletion regions on each side? What about the width of the depletion region on each side? Or, the total charge on each side? Can you qualitatively explain what you observe?
Let's apply a positive or negative voltage across this device and see what happens.
Doping Concentration (per cm3):
Applied Voltage (V)
Minority carrier concentration changes by many orders of magnitude depending on the applied voltage. Play with the applied voltage and see if you can qualitatively explain the trends you observe.
Doping Concentration (per cm3):
Applied Voltage (V)