Thermodynamic Driving Force Activated Phonon Scattering in InN

TL;DR

This study introduces a thermodynamic driving force coordinate to unify InN growth conditions, linking defect formation, Raman response, and structural coherence, enabling more controlled and defect-free material synthesis.

Contribution

The paper presents a universal thermodynamic coordinate for InN growth that correlates defect formation, Raman signals, and structural coherence across different process conditions.

Findings

Incorporation rate follows an activated trend with a 0.08 eV scale.

Raman response shows a crossover from defect sparse to defect rich regimes.

Structural coherence length remains constant at fixed driving force despite different reactor settings.

Abstract

Defect related disorder during InN growth is a major challenge for making high performance electronic and optoelectronic devices. This is partly because film quality is often described using reactor specific settings instead of general physical variables. In this study, we show that plasma assisted MOCVD growth of InN can be described using a single thermodynamic driving force coordinate. This coordinate brings together growth kinetics, defect sensitive Raman response and structural coherence across different process conditions. When we use this coordinate, the incorporation rate follows a universal activated trend with a kinetic scale of about 0.08 eV. Raman measurements show a clear crossover between a defect sparse and a defect rich regime, a disorder activated Raman metric increases quickly after the crossover, while an A1-LO control metric stays mostly the same. This suggests that short range lattice disorder, not long range polar coupling, dominates the defect activation process. X-ray diffraction shows that the out of plane coherence length stays the same for samples with the same driving force, even if reactor settings are very different. This supports the idea that structural coherence is organized by thermodynamics in this growth window. Finally, a simple kinetic Monte Carlo model using driving force biased incorporation and defect activation events matches the observed exponential trends and the two regimes, supporting the driving force approach. These results show that a transferable driving force coordinate can be used for plasma assisted InN growth and offer a quantitative way to achieve defect sparse growth conditions.