Unveiling the Pockels Coefficient of Ferroelectric Nitride ScAlN

TL;DR

This paper provides a theoretical and experimental analysis of the Pockels effect in ScAlN, showing that high levels of scandium doping can enhance its electro-optic properties beyond those of lithium niobate, promising for optical device applications.

Contribution

It offers the first comprehensive analysis of the Pockels effect in ScAlN, demonstrating potential for improved electro-optic performance with increased scandium doping.

Findings

Electro-optic coupling in ScAlN is weak at low Sc concentrations.

High Sc doping levels significantly enhance the Pockels effect.

ScAlN can surpass LiNbO₃ in electro-optic performance at high doping levels.

Abstract

Nitride ferroelectrics have recently emerged as promising alternatives to oxide ferroelectrics due to their compatibility with mainstream semiconductor processing. ScAlN, in particular, has exhibited remarkable piezoelectric coupling strength ($K^2$) comparable to that of lithium niobate (LN), making it a valuable choice for RF filters in wireless communications. Recently, ScAlN has sparked interest in its use for nanophotonic devices, chiefly due to its large bandgap facilitating operation in blue wavelengths coupled with promises of enhanced nonlinear optical properties such as a large second-order susceptibility ($\chi^{(2)}$). It is still an open question whether ScAlN can outperform oxide ferroelectrics concerning the Pockels effect -- an electro-optic coupling extensively utilized in optical communications devices. In this paper, we present a comprehensive theoretical analysis and experimental demonstration of ScAlN's Pockels effect. Our findings reveal that the electro-optic coupling of ScAlN, despite being weak at low Sc concentration, may be significantly enhanced and exceed LiNbO$_3$ at high levels of Sc doping, which points the direction of continued research efforts to unlock the full potential of ScAlN.