Modelling and optimization of GaN-based gamma-voltaic cells using a coupled Monte Carlo-TCAD radiation–device simulation framework

In this work, a GaN-based gamma-voltaic device is modeled and optimized using a coupled radiation–device simulation framework. Monte Carlo simulations are employed to model gamma energy deposition and radiation-induced lattice displacement within GaN, while TCAD simulations are used to analyze the resulting electric field distributions, charge transport, and current collection in multiple device architectures. Simulation results identify single-cell configurations capable of producing up to 39 μA/cm2 of current with an open-circuit voltage of 2.62 V, and stacked-cell architectures capable of producing up to 200 μA/cm2. The results highlight the importance of heavy, asymmetric doping, a moderately sized depletion region, and P⁺–p–n–N⁺ junction designs in maximizing charge collection efficiency. In addition, the impact of trap states and radiation-induced defects on device performance is examined, providing insight into degradation mechanisms in irradiated GaN gamma-voltaic devices.