Power semiconductors
In Baliga's figure of merit, used to compare materials for unipolar power devices, which material property has a particularly strong effect?
- ALattice constant
- BBreakdown field (it enters as the cube)
- CThermal expansion coefficient
Show answer and explanation
Answer: B. Breakdown field (it enters as the cube)
Baliga's figure of merit is ε μ Ec³, using the permittivity ε, mobility μ and breakdown field Ec, and indicates how low an on-resistance can be achieved for a given breakdown voltage. Because the breakdown field enters as the cube, SiC and GaN, with breakdown fields about ten times that of Si, have figures of merit orders of magnitude larger than Si.
- A. The lattice constant is not part of Baliga's figure of merit.
- B. Correct. The breakdown field enters as the cube.
- C. The thermal expansion coefficient is not part of Baliga's figure of merit.