Area 07
Wide-bandgap semiconductors for power electronics
SiC and GaN tolerate heat and overvoltage better than silicon. Traps, defects and interface transport.
Context
A grid with high solar penetration, exposed to hot ambient conditions and frequent atmospheric overvoltages, is exactly the use case where silicon power devices reach their limits. Silicon carbide and gallium nitride are the industrial answer; their failure physics remains open.
Fine characterisation and defect modelling govern the reliability of these devices. That is the question inverter manufacturers actually care about, and it can be addressed independently of fabrication.
Open questions
What the literature does not settle
Traps at the oxide/SiC interface: what is the chemical nature and energy distribution of the states that limit channel mobility in 4H-SiC transistors?
Threshold-voltage instability under bias and temperature: what trapping and detrapping kinetics, and what fraction of the drift is genuinely reversible?
Deep traps and current collapse in AlGaN/GaN heterostructures: where are the responsible traps located, and how do they couple to surface states?
Under combined thermal and electrical stress in tropical ambient conditions, does package and passivation degradation dominate intrinsic semiconductor degradation?
Which conduction mechanism (Poole–Frenkel, trap-assisted hopping, thermionic emission) describes leakage currents above 150 °C in these heterojunctions?
Feasibility
The devices are bought commercially; the work is in the characterisation. An I–V–T bench, C–V measurement and deep-level transient spectroscopy open the subject, and defect calculations run on the cluster.
Methods and facilities
- I–V–T and C–V characterisation versus temperature on commercial devices
- Deep-level transient spectroscopy and low-frequency noise measurements
- Bias-temperature ageing tests with drift monitoring
- Ab initio calculation of point defects and interface states
- TCAD drift-diffusion simulation coupled to thermal modelling
Target outcome
A characterisation and modelling capability for wide-bandgap power devices, useful to inverter manufacturers and high-solar-penetration grids, and the scientific basis for a future fabrication partnership.
Simulated production chain
SiC and GaN power module assembly lineFrom a DFT-computed interface defect to the junction temperature of an inverter at 40 °C ambient.Related areas
Computational physics
DFT, molecular dynamics, multiphysics simulation: electronic structure, phonon transport and point defects.
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Reliability physics in tropical environments
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