First-principles study of the phase competition, mechanical and piezoelectric properties of pseudo-binary (SiC)1-x(AlN)x alloy

Abstract

The ongoing search for new piezoelectric materials offering adequate balance between piezoelectric response and other application-relevant properties has led to the investigation of various alloy systems. In this work we study the alloy of the widely used AlN with SiC for their relative abundance, current use in other electronic applications and expected phase competition between wurtzite and other polymorphs, the likes of which has lead to some of the most interesting results notably between AlN and ScN. Here the pseudo-binary (SiC)_1-x(AlN)_x alloy is studied from first-principles over the entire composition range. Relevant crystalline phases are identified using the First-Principles Random Structure Sampling approach which, in accordance with previous bulk experiments, finds wurtzite, zincblende and rhombohedral phases to be the only statistically relevant phases of the alloy. Further study of these phases is done through Special Quasirandom Structures (SQSs) and, in the case of the wurtzite phase, predictions of the stiffness, piezoelectric and dielectric tensors. Analysis of these tensors is done through the scope of a Bulk Acoustic Wave (BAW) filter application, where trends and trade-offs between the c-axis acoustic velocity and piezoelectric response enable identification of relevant compositions.