The trigonal structure as a reference to access the spontaneous polarization of wurtzite crystals

TL;DR

This paper introduces a method using the trigonal structure as a reference to accurately determine the spontaneous polarization in wurtzite crystals, validated by comparison with experimental data and previous theoretical results.

Contribution

It proposes a novel reference structure approach for calculating spontaneous polarization in wurtzite materials, improving accuracy and consistency with experimental values.

Findings

Trigonal structure effectively used as a polarization reference.

Electronic polarization contribution exceeds ionic contribution.

Calculated polarization for GaN matches experimental data.

Abstract

The spontaneous polarization of wurtzite III-V nitrides XN (X=Al, Ga, In) and II-VI oxides YO (Y=Be, Zn) is investigated via first-principles computational methods. The modern treatment defines this quantity as the polarization difference between the investigated system and an appropriate reference state. We demonstrate that the trigonal structure can be used as a reference to determine the spontaneous polarization of wurtzite materials. We compare the current values with the widely-known zincblende results reported in the literature and find a very good agreement. It is shown that the electronic contribution of polarization is greater than the ionic one. Furthermore, we reproduce the experimental value of the spontaneous polarization of wurtzite GaN reported in a previous study. In order to do so, we calculate the spontaneous polarization for each type of stacking faults using periodic supercells and the Berry-phase method. This theoretical analysis leads to a value nearly identical to the experimental measurement.