| Summary: | In this work, Gallium Nitride (GaN)-based p-i-n diodes were designed using a computer aided design (TCAD) simulator for realizing a betavoltaic (BV) cell with a high output power density (<i>P</i><sub>out</sub>). The short-circuit current density (<i>J</i><sub>SC</sub>) and open-circuit voltage (<i>V</i><sub>OC</sub>) of the 17 keV electron-beam (e-beam)-irradiated diode were evaluated with the variations of design parameters, such as the height and doping concentration of the intrinsic GaN region (<i>H</i><sub>i-GaN</sub> and <i>D</i><sub>i-GaN</sub>), which influenced the depletion width in the i-GaN region. A high <i>H</i><sub>i-GaN</sub> and a low <i>D</i><sub>i-GaN</sub> improved the <i>P</i><sub>out</sub> because of the enhancement of absorption and conversion efficiency. The device with the <i>H</i><sub>i-GaN</sub> of 700 nm and <i>D</i><sub>i-GaN</sub> of 1 × 10<sup>16</sup> cm<sup>−3</sup> exhibited the highest <i>P</i><sub>out</sub>. In addition, the effects of native defects in the GaN material on the performances were investigated. While the reverse current characteristics were mainly unaffected by donor-like trap states like N vacancies, the Ga vacancies-induced acceptor-like traps significantly decreased the <i>J</i><sub>SC</sub> and <i>V</i><sub>OC</sub> due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the <i>P</i><sub>out</sub>. Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced <i>P</i><sub>out</sub> in BV cell.
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