Theoretical study of a high-efficiency GaP–Si heterojunction betavoltaic cell compared with metal–Si Schottky barrier betavoltaic cell

Abstract

In this work, energy converters, which contain a GaP–Si heterojunction and Si-based Schottky barrier diodes with Al, Ti, Ag, and W, are used to convert 2 μm-thick ⁶³Ni radioactive source energy into electrical energy. First, energy deposition distributions of the ⁶³Ni radioactive source in these converters are simulated by using the Monte Carlo method. Then, the electrical output properties of the ⁶³Ni/GaP–Si cell and ⁶³Ni/metal–Si cell are determined through the numerical calculation. For the ⁶³Ni/GaP–Si cell, with the optimized thickness of the GaP layer and doping concentration of Si, the maximum output power density and the conversion efficiency are 0.189 µW cm⁻² and 1.83%, respectively. For the Si-based Schottky barrier cells with Al, Ti, Ag, and W, the ⁶³Ni/Al–Si cell has the best electrical output properties with the same thickness of the metal layer and doping concentration of Si. When the thickness of metal Al is 0.1 µm and the doping concentration N_a is 1 × 10¹³ cm⁻³, the maximum output power density and the conversion efficiency are 0.121 µW cm⁻² and 1.18%, respectively. The calculation results indicate that the ⁶³Ni/GaP–Si battery has better electrical output properties than the ⁶³Ni/Al–Si Schottky battery. These results are valuable for fabricating practical batteries.