Ultrawide Bandgap BN based Vertical Power Diodes via TCAD Simulation

Boron nitride (BN) material is an emerging ultrawide bandgap (UWBG) semiconductor with great promise for applications in power electronics, ultraviolet (UV) photonics, and quantum photonics. The current most mature phase of BN, hexagonal BN, has a large bandgap of 6.0 eV and has attracted a lot of interest owing to its unique physical properties. Due to its high thermal conductivity of 390 W/(K●m), high breakdown electric field of ~12 MV/cm, and high carrier mobilities, h-BN is also an attractive candidate for high-performance high power high voltage power electronic devices. However, it is still very challenging to produce high quality thick h-BN layers due to the technical difficulties in materials epitaxy and doping, which has hindered the development of BN devices. Furthermore, vertical architecture is usually adopted in high voltage power devices due to high current and voltage handling capability, immunity to surface issues and degradation and excellent heat dissipation. However, there are very few reports on BN vertical power devices and the performance limit of these devices is still not clear.<br/>In this work, we use technology computer-aided design (TCAD) simulation to theoretically investigate the electrical performance of ultrawide bandgap BN-based vertical power diodes. Three configurations of h-BN power diodes were investigated, including vertical h-BN Schottky barrier diode (SBD), vertical h-BN PN diode, and vertical h-BN/AlN PN diode. The electrical properties of the three diodes were comprehensively investigated, including the band diagrams, forward and reverse characteristics for different doping concentrations and layer thicknesses. The h-BN material properties were defined in Silvaco Atlas, including bandgap, effective masses of electron and hole, permittivity, impact ionization coefficient, electron affinity, mobilities, carrier lifetimes, donor and acceptor activation energies from the previous reports of h-BN. All the substrates’ doping concentrations were set to be 5×10¹⁸ cm⁻³as ohmic contact layers for P-type and N-type. The h-BN power diodes showed excellent performance, especially for breakdown behaviors. The h-BN SBDs with a 5 μm drift layer showed a turn-on voltage of 0.5 V for Pt Schottky contact and breakdown voltages over 450 V. The h-BN PN diode with a 2.5 μm drift layer showed a turn-on voltage of 6.2 V and a breakdown voltage over 3 kV, the critical electric field is calculated to be 13.6 MV/cm. The h-BN/AlN heterojunction PN diode with a 2.5 μm AlN drift layer showed a turn-on voltage of 5.8 V and breakdown voltages over 2 kV. This work provides a theoretical understanding on the device principles of vertical BN power diodes, which can serve as a useful reference for the future development of efficient and robust BN power electronics.