Semiconductor devices lab
Explore semiconductor doping, junction formation, diode conduction and rectification using carrier and circuit models.
Learning goals
- Explain energy bands, intrinsic conduction and how temperature and light change semiconductor resistance.
- Explain n-type and p-type doping, donor and acceptor levels and majority carriers.
- Explain p-n junction formation and bias, and analyse diode, LED, Zener, rectifier-smoothing, sensor and transistor-switching circuits.
A p–n junction with no bias of 0.00 V. The depletion region is 0.430 µm wide and the current is 0 A.
- Free electrons drawn
- 9
- Holes drawn
- 1
- Majority carriers
- electrons
- ni relative to 300 K
- 1.0
- Depletion width, W
- 0.430 µm
- Barrier, Vbi − V
- 0.71 V
- Current, I
- 0 A
- Peak output p.d.
- 5.30 V
- Peak supply p.d.
- 6.0 V
Try this
0 of 4 doneDope the silicon so that electrons are the majority carriers. (not done yet)
Each phosphorus atom has a fifth outer electron that is free to move. The phosphorus ion it leaves is fixed and positive, so the crystal stays neutral.
Heat pure silicon from 300 K to 400 K. What happens to the carriers? (not done yet)
Hundreds of times more electron–hole pairs: the resistance falls steeply, as in a thermistor.
Reverse-bias the junction by at least 3 V. (not done yet)
The depletion region widens and the barrier grows, so the majority carriers cannot cross: only a tiny leakage current flows.
Compare the half-wave and full-wave rectifiers. (not done yet)
A single diode passes only the positive half-cycles. The bridge steers both halves through the load in the same direction.
You’ve tried every task.