F. Brunner, E. Brusaterra, E. Bahat-Treidel, O. Hilt, and M. Weyers

Published in:

phys. stat. sol. (rrl), vol. 18, no. 11, pp. 2400013, doi:10.1002/pssr.202400013 (2024).

Abstract:

The development of processes for epitaxial growth of vertical gallium nitride (GaN) drift layers enabling 1.2 kV breakdown voltage on low-cost sapphire substrates is presented in comparison to GaN bulk substrates. The targeted blocking capability demands drift layers with a thickness of 10 μm and low but controllable n-type doping. Using a growth rate of 2.5 μm h^-1 the concentration of unintentionally incorporated carbon is sufficiently low to adjust the n-type carrier concentration to ≈1 × 10¹⁶ cm^-3 for all types of substrates. To assess GaN drift region properties in terms of forward bias conductivity and reverse bias blocking strength, a quasi-vertical p-n-diode structure is utilized. Bow reduction of GaN-on-sapphire structures is achieved using a stealth laser scribing process. Breakdown voltages higher than 1600 V and a specific on-state resistance as low as 0.7 mΩ cm² are obtained with diodes fabricated on GaN substrates. Similar structures grown on sapphire show breakdown voltages of about 1300 V due to higher levels of current leakage. Comparing different types of substrates, a direct correlation between dislocation density in the drift layer with the leakage current in p-n diodes is deduced.

Keywords:

breakdown voltages, carbon incorporation, dislocation density, epitaxy, on-state resistance, silicon doping, vertical power devices

© 2024 The Authors. physica status solidi (RRL) Rapid Research Letters published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Rightslink® by Copyright Clearance Center

Full version in pdf-format.