Experiment 8
Semiconductor Band Gaps from LED Simulations
Visualize electron-hole recombination and determine Planck's constant from LED threshold voltages.
Material Selection
Wavelength (λ)660 nm
Threshold (V0)1.88 V
Key Equations
eV₀ ≈ Eg ≈ hc/λ
The slope of V₀ vs 1/λ yields hc/e, from which Planck's constant h can be determined.
Recombination & Photon Emission
Direct Band Gap
Planck's Constant Determination (V₀ vs 1/λ)
Data points added: 0 / 6
Task: Photon Color
Click through the materials and observe the emitted photon color. Note how the energy of the photon (and thus the threshold voltage) increases as wavelength decreases.
Teaching Connection
LEDs are a perfect "real-world hook". Every screen pixel is a precisely engineered semiconductor junction. Quantum mechanics literally controls the color of our world.
Reflection Questions
- Why do indirect-gap semiconductors like Silicon make poor LEDs?
- Explain the linear relationship between the threshold voltage and the reciprocal of the wavelength.
- Estimate the indium fraction needed in InGaN to produce a specific green wavelength.