Passivation of Surface and Interface States in AlGaN/GaN HEMT Structures by Annealing |
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Authors: | Hyeongnam Kim Michael L Schuette Jaesun Lee Wu Lu James C Mabon |
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Affiliation: | (1) Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA;(2) Center for Microanalysis of Materials, Frederick Seitz Materials Research Laboratory, 104 S. Goodwin Avenue, Urbana, IL 61801, USA |
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Abstract: | The Ni/AlGaN interfaces in AlGaN/GaN Schottky diodes were investigated to explore the physical origin of post-annealing effects
using electron beam induced current (EBIC), current–voltage (I–V) characteristics, and X-ray photoelectron spectroscopy (XPS). The EBIC images of the annealed diodes showed that the post-annealing
process reduces electrically active states at the Schottky metal/AlGaN interfaces, leading to improvement of diode performance,
for example a decrease in reverse leakage current and an increase in Schottky barrier heights. Pulsed I–V characteristics indicate the Fermi level is up-shifted after annealing, resulting in a larger sheet carrier density at the
AlGaN/GaN interface. Unintentional oxidation of the free AlGaN surface during the post-annealing process, revealed by XPS
analysis, may prevent electron trapping near the drain-side of the gate edges. We suggest that the post-annealing process
under an optimized conditions can be an effective way of passivating AlGaN/GaN heterojunction field-effect transistors. |
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Keywords: | AlGaN/GaN HEMT post-gate annealing surface/interface states passivation |
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