Diffusion‐Governed Growth Mechanisms of Epitaxial GaAs Islands on CMOS‐Compatible Si(001) Nanotip Arrays

Abstract

ABSTRACT In this work, we investigate the diffusion‐controlled growth mechanism and kinetics of gallium arsenide (GaAs) islands on CMOS‐compatible Si(001) nanotip wafers using nanoheteroepitaxy by gas‐source molecular beam epitaxy. Si nanotips embedded in a silicon dioxide (SiO 2 ) matrix serve as predefined nucleation sites. The influence of pitch size (center‐to‐center distance between nanotips) on island growth is analyzed. Energy‐dispersive X‐ray spectroscopy (EDX) and scanning electron microscopy (SEM) confirm selective GaAs growth exclusively on the nanotips, without parasitic nucleation on the surrounding SiO 2 . Statistical analysis of top‐view SEM images reveals a ∼29% reduction in projected island area between 0.5 and 2 µm pitch arrays. The pitch dependence identifies three surface‐diffusion‐controlled regimes: (i) collective diffusion‐mediated growth for pitches smaller than the Ga adatom diffusion length, (ii) a crossover regime at comparable pitch and diffusion length, and (iii) diffusion‐limited isolated growth for larger pitches. These regimes demonstrate that lateral Ga adatom transport on the SiO 2 mask determines material redistribution and incorporation. From the pitch‐dependent size transition, a Ga surface diffusion length of 0.8–0.9 µm is extracted under As‐rich conditions at 580°C. Thus, array geometry directly controls mass transport, incorporation efficiency, and island size. GaAs NHE therefore enables kinetic control through pitch‐dependent surface diffusion.