Leakage Suppression Across Temperature in Al1-xScxN Thin Film Ferroelectric Capacitors through Boron Incorporation

TL;DR

This study demonstrates that incorporating boron into AlScN thin films significantly reduces leakage currents and maintains ferroelectric properties up to 600°C, making them suitable for high-temperature applications.

Contribution

The paper introduces AlBScN thin films with boron incorporation, achieving suppressed leakage and stable ferroelectricity at high temperatures, a novel advancement over existing ferroelectric materials.

Findings

Leakage currents are over two orders of magnitude lower than in AlScN.

Ferroelectric switching persists up to 600°C with stable polarization.

Coercive fields decrease linearly with temperature.

Abstract

This paper presents high-temperature ferroelectric characterization of 40~nm Al$_{1-x-y}$B$_x$Sc$_y$N (AlBScN) thin film capacitors grown by co-sputtering Al$_{0.89}$B$_{0.11}$ and Sc targets onto Pt(111)/Ti(002)/Si(100) substrates. Structural analysis confirmed a c-axis-oriented wurtzite structure with a low surface roughness of 1.37~nm. Ferroelectric switching, characterized by positive-up-negative-down (PUND) measurements up to 600~$^\circ$C, exhibited a linear decrease in coercive fields from 6.2~MV/cm at room temperature to 4.2~MV/cm at 600~$^\circ$C, while remanent polarization remained stable with temperature. Direct current I-V measurements highlight a significant suppression of leakage currents, over two orders of magnitude lower compared to AlScN capacitors fabricated under similar conditions. These results position AlBScN thin films as strong candidates for ferroelectric applications in extreme environments.