Experiment 6
The p-n Junction and Diode Characteristics
Visualize the band diagram of a p-n junction under bias and plot the rectifying I-V characteristic.
Controls
Key Equations
Shockley Equation:
I = I0 [exp(eV/ηkBT) - 1]
Forward bias (V > 0) reduces the potential barrier, allowing exponential current flow.
Band Diagram Visualization
Potential Barrier: 0.70 eV
I-V Characteristic Curve
Task: Biasing Effects
Observe the band bending. Under Forward Bias(V > 0), the barrier height decreases. Under Reverse Bias(V < 0), the barrier increases and the depletion region widens.
Teaching Connection
The p-n junction is the building block of modern electronics. Use this to show students why a diode acts as a "one-way street" for electricity.
Reflection Questions
- Why does the forward current increase dramatically when temperature increases?
- Compare the threshold voltages for Si, Ge, and GaAs. Which has the largest band gap?
- What happens to the depletion region width under reverse bias?