- Depletion layer prevents the diode from conducting current
- Applying an external voltage can either:
- increase size of the depletion layer (decrease conductivity)
- decrease size of the depletion layer (increase conductivity)
- A diode is forward biased when the positive terminal of the battery is connected to the p-side of the junction. The depletion layer becomes smaller and current can flow
- A diode is reverse biased when the positive terminal of the battery is connected to the n-side of the junction. The depletion layer becomes larger and current cannot flow
Diode current-voltage characteristic
- In striking contrast to the symmetric behavior of resistors that obey Ohm’s law and give a straight line on an I–V graph, a p-n junction conducts much more readily in the direction from p to n than the reverse.
- The current I flowing through a diode can be expressed as:
where
I0: Saturation current (small)
V: Voltage across diode
e: Electron charge
T: Temperature (in K)
k: Boltzmann constant (k = 1.38×10−23 J K-1)
