Molecular dynamics simulation of AlGaN film deposition on GaN template: unraveling the roles of temperature and Al/Ga flux ratio in growth mechanism

Abstract

AlGaN/GaN heterostructures are cornerstone materials for high-performance devices like High Electron Mobility Transistors (HEMTs), yet their fabrication remains largely empirical. A critical bottleneck is the lack of atomic-scale theoretical frameworks to clarify how deposition parameters tune key heterostructure properties—dislocation density, structural composition, surface roughness, in-plane stress—hindering the rational optimization of device quality. To fill this gap, we present a molecular dynamics (MD)-based atomic-scale investigation of AlGaN deposition on GaN templates, aiming to uncover the unelucidated mechanisms that quantify the correlative trends between such parameters and properties at the atomic level. Key findings include three fabrication-relevant insights: 1) For temperatures (1200–1800 K), we identified 1600 K as the optimal value, featuring peak crystalline quality and monotonic roughness reduction—driven by enhanced adatom mobility. Our work clarifies this mobility's synchronous regulation of the two key properties in systems like AlGaN/GaN heterostructures, offering new atomic-scale insights into their correlation. 2) For Al/Ga flux ratios (1:4 to 3:1), Al/Ga = 1:3 yields highest crystallinity; Al/Ga ≥1 surfaces are smoother than Al/Ga <1. This divergence comes from clarified atomic process: Ga-rich conditions promote Ga desorption, while higher Al suppresses it—unhighlighted before. 3) We confirmed that in-plane tensile stress (arising from lattice mismatch) is dominant; further, our molecular dynamics (MD) simulations uniquely quantify how temperature and flux modulate the stress magnitude at the atomic interface. This work's innovation is translating atomic deposition dynamics into actionable AlGaN/GaN guidelines—addressing trial-and-error/theory disconnect. Findings guide parameter optimization, accelerating high-quality heterostructure synthesis for next-generation HEMTs.