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(out)). The short-circuit current density (J(SC)) and open-circuit voltage (V(OC)) 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(i-GaN) and D(i-GaN)), which influenced the depletion width in the i-GaN region. A high H(i-GaN) and a low D(i-GaN) improved the P(out) because of the enhancement of absorption and conversion efficiency. The device with the H(i-GaN) of 700 nm and D(i-GaN) of 1 × 10(16) cm(−3) exhibited the highest P(out). 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(SC) and V(OC) due to an increase in recombination rate. As a result, the device with a high acceptor-like trap density dramatically degenerated the P(out). Therefore, growth of the high quality i-GaN with low acceptor-like traps is important for an enhanced P(out) in BV cell.