Quick summary
A power transistor alternates between conducting current and blocking voltage. Gallium nitride (GaN) can tolerate a stronger electric field before breakdown than silicon, so designers can reduce the thickness or resistance of the voltage-blocking region. Fast switching can shrink converters, but real performance depends on device geometry and the complete power module.
Why wide bandgap matters
The bandgap is the energy separating bound and conducting electron states. GaN’s wider bandgap contributes to a high critical electric field. In principle, this supports high breakdown voltage with lower on-resistance, reducing conduction loss. High electron mobility in common GaN heterostructures also supports rapid switching.
Where breakdown begins
Electric field is not uniform. It can crowd near gate edges, contacts and material defects, producing leakage and premature breakdown. Field plates spread the potential, while buffers, passivation and device dimensions shape the field. Charge-balanced structures arrange positive and negative regions so their fields partially cancel and the blocking voltage rises without an excessive resistance penalty.
Device test versus converter performance
Breakdown voltage is often measured at low current under specified laboratory conditions. A converter also needs useful current, low on-resistance, a gate driver, isolation, thermal management and protection from switching spikes. Parasitic inductance in packaging can erase some speed advantage or overstress the device.
Why growing GaN on silicon helps and hurts
Silicon substrates can lower cost and use larger established wafers, but GaN and silicon differ in lattice spacing and thermal expansion. Buffer layers manage stress and defects, yet wafer bow, cracking, leakage and variation can affect yield and reliability. A successful small device does not prove a high-yield manufacturing process.
Reliability under real stress
Power switches face repeated voltage, current and temperature cycles. Trapping can change resistance dynamically, while gates and buffer layers can degrade. Qualification therefore needs accelerated stress, switching tests and models connecting laboratory ageing with expected field life.
Reality check
Withstanding 3.4 kilovolts does not mean continuously switching that voltage in a commercial converter. Check the test current, device area, on-resistance, switching conditions and failure definition. A material record can coexist with unresolved packaging, yield and lifetime problems.
What would demonstrate practical value?
Look for converter-level efficiency, power density, thermal performance, repeated device yield and qualification under the intended voltage and current. The strongest comparison uses the same function and conditions against modern silicon carbide or silicon, not an outdated baseline.
