The triggering mechanism for cosmic ray neutron-induced single-event burnout (SEB) in silicon insulated-gate bipolar transistors (IGBTs) and diodes was investigated by white neutron-irradiation experiments and transient device simulations. Electron-hole pairs are generated along the tracks of recoil ions produced by nuclear spallation reactions between incident neutrons and the constituent nuclei of the device. In the vicinity of the n⁻/n⁺ interface, the resulting dynamic current causes an increase in the electron density, and the space charge effect of the carriers leads to an increase in the peak electric field. In an IGBT, the onset of impact ionisation at this interface can cause a parasitic transistor to switch on. In the case of diodes, the electric field distribution leads to diode secondary breakdown. Therefore, impact ionisation at the n⁻/n⁺ interface is essential for triggering SEB. In this study, analytical equations are derived for the local rise in temperature during SEB. The local temperature rise is proportional to the energy, defined in terms of the product of the applied voltage and the total avalanche charge. The diameter of the damage region estimated using these equations is similar to the size of the observed annular voids.