Effect of Particles Incidence Angle on GaN Epitaxial Thin Films for Optoelectronic Devices by Molecular Dynamic Simulation

GaN materials are widely used in optoelectronic devices. Molecular beam epitaxy is very important in the field of material growth and the angle at which molecules or atoms are incident on the substrate has a significant effect on the crystal quality and surface morphology of the epitaxial film. There are relativity few microscopic research on the impact of various incident angles affecting the quality of GaN epitaxial film. In this work, the molecular dynamics is utilized to investigate deposition process at different incident angels of GaN film. The crystal structure evolution, surface topography, roughness, dislocation distribution, atomic directional stress distribution and atomic density are calculated and analyzed. The results show that the epitaxial film roughness remains almost unchanged when the angle of incidence increases from zero to
$15^{\circ}$
. The surface roughness of the epitaxial film increases rapidly as the molecules or atoms incident angle continues to increase from
$15^{\circ}$
. When the angle of incidence is smaller than
$45^{\circ},$
the atomic density in each layer decreases slowly from the 0th layer to the 18th layer of the film and then the number of atoms decreases rapidly. While when the incident angle of particles is greater than
$45^{\circ}$
the number of particles in each layer decreases rapidly from layer 0. For the z-direction stress, the stress of the atomic layer decreases the fastest at the particle incident angle of
$75^{\circ},$
and the atomic energy reaches the minimum stress at about the 10th layer. While for the biaxial stress, the atomic energy reaches the minimum at the incident angle range from
$0^\circ$
to
$30^{\circ}$
.