Design and Analysis of Gallium Nitride-Based p-i-n Diode Structure for Betavoltaic Cell with Enhanced Output Power Density.

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 (P). The short-circuit current density (J) and open-circuit voltage (V) 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 (H and D), which influenced the depletion width in the i-GaN region. A high H and a low D improved the P because of the enhancement of absorption and conversion efficiency. The device with the H of 700 nm and D of 1 × 10 cm exhibited the highest P. 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 J and V due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the P. Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced P in BV cell.