Time-resolved cathodoluminescence measurement of the effects of α-particle-related damage on minority hole lifetime in free-standing n-GaN.

Time-resolved cathodoluminescence using 30 keV ultrafast electron pulses has been used to perform direct measurements of the minority hole lifetime τ h as a function of 3.7 MeV α -particle fluence in high-quality free-standing n-type GaN substrates. The lifetime damage factor K calculated from these measurements was found to monotonically decrease from 6.9 × 10⁻² to 6.4 × 10⁻⁴ cm² s⁻¹ ion⁻¹ with increasing α -fluence from 10⁸ to 10¹² cm⁻², implying a reduction in trap cross section and/or an aggregation of α -induced traps. The small, ∼ 200–300 nm, hole diffusion length estimated from the minority hole lifetime for the highest α -fluence necessitates the deployment of α -voltaic device strategies and architectures that emphasize depletion and drift over diffusion for effective charge collection and optimal power conversion efficiency. [ABSTRACT FROM AUTHOR]