ISBN 978-3-8439-5454-9

978-3-8439-5454-9, Reihe Elektrotechnik

Muhammad Fahlesa Fatahilah
3D GaN Nanowire Platform for Vertical Electronics and Sensors

210 Seiten, Dissertation Technische Universität Braunschweig (2024), Softcover, A5

Zusammenfassung / Abstract

Vertical GaN nanostructure FETs are promising because they can be integrated efficiently, and their large sidewall surfaces are usable as a channel area.

The direct quantitative and qualitative performance comparisons of vertical FETs–based on vertical GaN nanowires with different numbers (i.e., 1–100) and diameters (i.e., 220 nm–640 nm) have demonstrated how such architectures can be used for a future vertical electronic integration.

A hybrid top-down approach utilizing dry and wet chemical etching was applied to fabricate vertical GaN nanowires FETs on GaN/sapphire templates with specific doping profiles epitaxial thin films. FETs’ fabrication involves an n-p-n GaN template with an inverted p-channel, wrap-around gate, and top drain bridging contact structure. Based on the electrical parameter of the NWs, a threshold voltage (Vth) of ~6.5 V has been obtained. The highest and very stable Vth so far for c-axis GaN NW MOSFETs was sufficient for safely operating devices in a normally-off or enhancement-mode (E-mode).

Nanowires are furthermore interesting architectures for applications beyond power electronics. In particular, the GaN NWs were further investigated with nanoindentation, demonstrating a potential for further development in the direction of GaN NW piezo matrix sensors. Again, the low-power GaN NW FETbased sensors developed used an uncovered Al2O3 on the drift region as a sensing material supported by a wrap-around gate for an ethanol gas as a sensing target.

Ethanol gas could be detected with concentrations down to the ppm level, with response and recovery time lower than 2 s dissipating power as low as µW. It demonstrated an excellent sensing performance of ultra-low-power vertical GaN NW MOSFET-based sensors.

In summary, GaN nanowire technology is suggested to be not only an interesting architecture for power electronics but also another approach toward micro-scale future electronic sensors.