Thermodynamic Analysis of Hybrid Chemical Vapor Deposition of Transition-Metal-Alloyed Group-III-Nitride ScAlN Piezoelectric Semiconductor Films

We introduce hybrid chemical vapor deposition (HybCVD) employing chloride, an elemental source, and hydride for the precursors of the group-III element, transition-metal element, and nitrogen, respectively, for obtaining ScAlN thin films to address the technical challenges in current techniques associated with film quality and manufacturability. For the new deposition technique, we numerically investigate the thermodynamics of precursors and vapor-solid reactions to evaluate the suitability of the precursors and controllability of the alloy composition depending on various precursors and deposition conditions. The AlCl3 precursor is needed to provide a high precursor input while protecting the CVD system. An elemental Sc source precursor is capable of providing a high precursor input and enough driving force for ScN formation. For the film deposition, the Sc composition of the film slightly decreases with increasing V/III ratio and growth temperature, while its change by the mixture ratio of inert gas and hydrogen in the carrier gas is negligible. The Sc composition in the alloy can be accurately controlled by the mixture ratio of the cation precursors. HybCVD offers the potential for both the high material quality and low-cost manufacturing of transition-metal-alloyed III-N thin films to maximize their expected benefits for highly functional piezoelectric materials in a wide range of applications.

Automated summary

HybCVD technique using chloride and hydride precursors is introduced to obtain ScAlN thin films, addressing the challenges in film quality and manufacturability. Numerical analysis of precursor thermodynamics and vapor-solid reactions evaluate the precursors' suitability and alloy composition control.