S. Chevtchenko¹, E. Brusaterra¹, I. Ostermay², D. Sudau² and O. Hilt¹

Published in:

Semicond. Sci. Technol., vol. 40, no. 9, pp. 095016, doi:10.1088/1361-6641/ae03e5 (2025).

Abstract:

This work reveals how the number of active interface trap states in an AlGaN/GaN epitaxial structure can be influenced by SiN_x passivation without modifying the semiconductor /passivation interface. We compare the density of interface trap states for passivations comprising SiN_x layers with different built-in compressive stresses of 46 MPa and 956 MPa. Metal–insulator–semiconductor capacitors were fabricated for electrical characterization. As the insulator we used a single and bi-layer stack of SiN_x with two thicknesses—100 nm and 150 nm in total for each stack. Capacitance–voltage, capacitance–frequency and conductance–frequency measurements were performed. The extracted density of interface traps remained in the range from 2.6 × 10¹¹ cm⁻² to 4.0 × 10¹¹ cm⁻² for the structures with tested SiN_x layers. These minor differences in the density of states do not indicate an advantage from any SiN_x passivation stack variation used in our experiment. On the other hand, the trap activation electric field changed from 0.198 V nm⁻¹ for single-layer to 0.277 V nm⁻¹ for bi-layer passivation, thus reducing the trap interaction to the two-dimensional electron gas. We propose to use this effect as an effective method to control the active interface trap states in GaN-based transistors.

Keywords:

AlGaN/GaN, passivation, SiN_x, stress, interface traps, density of states

© 2025 The Author(s). Published by IOP Publishing Ltd
Original content from this work may be used under the terms of the (Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Full version in pdf-format.