Abstract:
The dependence of the properties of buffer layers at the interfaces of silicon-ferroelectric and silicon-high-k-insulator on the material and thickness of the insulator deposited on the substrate is analyzed. Films of ferroelectric Ba$_{0.8}$Sr$_{0.2}$TiO$_3$ and high-k-insulator HfO$_2$ with a set of thicknesses from 20 to 150 nm and the same sizes of field contacts were deposited on the same plate of n-type silicon with natural oxide. It turned out that the capacitance values in each of the saturation regions of the high-frequency capacitance-voltage characteristics for all thicknesses of the insulating layer are close to each other. For objects with high-k-insulator, a decrease in capacitance with an increase in the thickness of the insulator was observed. The graphs of the dependences of the band bending in the semiconductor on the field voltage and the spectral density of electron traps in the buffer layers of the structures with HfO$_2$ on the energy in the silicon band gap are constructed. It is shown that the concentration and spectrum of electron traps at the contact of silicon with the ferroelectric are practically independent of the thickness of the insulating layer. The buffer layer at the interface of silicon with a high-k dielectric changes its properties significantly with increasing thickness of the insulator – the spectral curve of electron traps shifts deep into the band gap of the semiconductor, expands, and its minimum value decreases.
Keywords:silicon-ferroelectric/silicon-high-k-insulator interfaces, transition (buffer) layer, electron traps, high-frequency capacitance-voltage characteristics.
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