Proceedings of nanoGe Fall Meeting19 (NFM19)
DOI: https://doi.org/10.29363/nanoge.nfm.2019.148
Publication date: 18th July 2019
Scanning Kelvin Probe Microscopy (SKPM) resolves surface potentials on the nanoscale, which translate into the work function distribution of the sample as well as the distribution of additional charge carriers upon electronic excitation.[1] For quantitative analysis, frequency modulated (FM) SKPM methods have shown the highest accuracy. Heterodyne FM-SKPM in particular allows for fast scanning and exhibits low topographic crosstalk.[2] A quantitative visualization of work function and charge carrier distribution is especially of interest for the semiconductor-based industry (transistors, solar cells, etc.) to locate bottlenecks in device performances.
In this study, we investigated dynamic charging processes on active transistor devices (InAlN/GaN HEMT with LG = 100 nm) via a line-by-line heterodyne SKPM approach to acquire transient potential signals with a time resolution of around one second, while simultaneously recording macroscopic current-voltage (IV) characteristics on the same devices. During switching, some of the transistors exhibited a slow charging over several minutes in their IV response. Via time-resolved SKPM, we located the spatial origin of the slow charging in the gate-drain area of the transistor, where we observed a change in surface potential transients coinciding with the macroscopic IV transients. The observed charging could be caused by slow trapping mechanisms located either at the semiconductor/dielectric interface or the bulk dielectric passivation (PECVD SiOx or SiNx).
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