ShaneLogic/cuinse2-cigs-material-properties

CuInSe2/CIGS Material Properties and Band Gap Calculation

When to Use

• Determining doping type (p-type vs n-type) for CuInSe2 or CIGS materials
• Calculating band gap energy for Cu(In1-xGax)Se2 alloys
• Accessing fundamental material constants for chalcopyrite semiconductors
• Planning processing conditions (annealing atmosphere, composition)

Material Constants (CuInSe2)

| Property | Value | |----------|-------| | Crystal Structure | Chalcopyrite | | Lattice Constant a | 5.78 Å | | Lattice Constant c | 11.62 Å | | Band Gap (Eg) | 1.04 eV | | Melting Temperature | 986 °C | | Density | 5.75 g/cm³ | | Thermal Expansion (a-axis) | 11.23×10⁻⁶ /K | | Thermal Expansion (c-axis) | 7.90×10⁻⁶ /K | | Electron Effective Mass | 0.08 m₀ | | Heavy Hole Effective Mass | 0.72 m₀ | | Light Hole Effective Mass | 0.09 m₀ |

Doping Type Determination

For CuInSe2:

1. Check copper composition:

   • If excess Cu present → ALWAYS p-type

2. If indium-rich:

   • Doping type depends on Selenium (Se) content
   • Can be p-type or n-type

3. Apply annealing effects:

   • High pressure Se atmosphere → n-type converts to p-type
   • Low Se pressure → p-type converts to n-type

For CuGaSe2:

• ALWAYS p-type (regardless of composition or annealing)

Mobility Ranges:

• Hole mobility (Epitaxial): Up to 200 cm²/Vs
• Electron mobility (Crystals): 90 to 900 cm²/Vs
• Solar Cell practical values: 5–20 cm²/Vs

Band Gap Calculation for Cu(In1-xGax)Se2

Use the empirical quadratic equation:

Eg(x) = (1-x)·Eg(CuInSe2) + x·Eg(CuGaSe2) - b·x·(1-x)

Parameters:

• Bowing parameter b = 0.264
• Eg(CuInSe2) = 1.035 eV
• Eg(CuGaSe2) = 1.68 eV
• x = Ga fraction (0 ≤ x ≤ 1)

Constraints:

• Valid only for thin films with In,Ga alloy
• Composition range: 0 ≤ x ≤ 1

See references/band-gap-calculation-details.md for detailed calculation examples.