Efficiency limit for diamond metal/intrinsic/p-type Schottky barrier-based betavoltaic cells

Abstract

Diamond materials hold great potentials with favorable characteristics for betavoltaic cells, thanks to their simple structure, high conversion efficiency, and radiation robustness. However, to explore its efficiency limit is greatly hindered by the material growth, doping techniques, and device design as well. In this work, a device model based on a diamond metal/intrinsic/p-type (MIP) Schottky barrier architect is analyzed for an accurate prediction of the efficiency limit for the betavoltaic cell based on such a structure. The study takes various factors of significance into account on the betavoltaic cell device characteristics, including the radiation source, thickness and doping concentration of the intrinsic layer, metal work function, as well as the metal/diamond interface traps and traps in the bulk. The current–voltage characteristics and fundamental parameters of the betavoltaic cells are thoroughly analyzed. According to our results, an open-circuit voltage of 2.04 V, a short-circuit current density of 87 nA·cm−2, and a fill factor of 0.9 for the diamond MIP betavoltaic cell can be achieved, which give a maximum energy conversion efficiency of 10.7%, at optimal conditions using 50 nm thick Al metal as the contact layer, 9 μm thick and 1 × 1014 cm−3-doping intrinsic layer, and 10 μm thick and 2 × 1017 cm−3-doping p-layer under a 2 μm 63Ni irradiation. This work also discusses the impact of the interface/bulk traps on the barrier heights of practical Schottky diodes and the device's performance as well.