First-principles Study On Epitaxial Growth Of Silicon-based Gallium Nitride Materials

GaN material^[1]has been hailed as the second most important semiconductor material after silicon materials,and has been widely used in semiconductor devices such as light-emitting diodes and field effect transistors^[2].GaN as a wide bandgap semiconductor with direct energy gap^[3]has great advantages.It requires heterojunction epitaxial growth on sapphire?Al₂0₃?or silicon carbide?SiC?since GaN has no homogeneous substrate^[4].However,sapphire has poor thermal conductivity and SiC manufacturing costs are high.Therefore,Si is the most promising substrate choice because of its low price,good electrical and thermal conductivity and complete industrial production^[5].However,due to lattice mismatch and thermal mismatch between Si and GaN,a transition layer of AlN is required for epitaxial growth of GaN on Si-based^[6].Research reports^[7,8]show that the aluminum layer is pre-plated before the transition layer of Al-based epitaxial growth of AlN,and the grown GaN has high flatness and surface dislocation density is significantly reduced.But the specific theoretical mechanism has not been established.This paper uses first-principles calculation based on density functional theory,the adsorption sites and diffusion energy barriers of Al atoms on the clean,H-terminate and Cl-terminate Si?100?and Si?111?surfaces calculated by VASP simulation.Adsorption behavior of Ga?In and N atoms on the relevant surface.The main research contents and research results are as follows:1.On the surface of Si?100?treated by different methods,the most stable position of Al atom adsorption is different,and the diffusion path is different:on the surface of clean Si?100?,Al is easily adsorbed in the trench and zigzagged along the trench.On the H-terminate or Cl-terminate surface,Al is easily adsorbed at the H position at the top of the dimer column,and diffuses in a straight line at the top of the dimer column.2.The Si?111?surface terminated by different methods has the same stable position for the adsorption of Al atoms.The diffusion path is similar,and it is easy to adsorb to the Top position?T₂ site?of the second Si atom,along T₂ diffusion to H?Hollow site?.3.Regardless of Si?100?or Si?111?surface,H-terminate and Cl-terminate Si surfaces are effective in reducing the diffusion energy barrier of Al atoms.4.The stable adsorption sites of Ga atoms on the clean,H-terminate and Cl-terminate Si?111?surfaces are the same,all of which are T₂ sites;the stable position of In atoms adsorbed on the clean Si surface is T₂.The site of stable adsorption on the surface of H-terminate or Cl-terminate Si?111?is the H site.Both H-terminate or Cl-terminate Si?111?surfaces can effectively reduce the adsorption energy of metal atoms on the surface of Si?111?and play a role in protecting the substrate.5.The adsorption of N atoms on the surface of clean,H-terminate and Cl-terminate Si?111?will destroy the Si-Si bond between the T₁ and T₂sites.Distinguish the six-membered ring of Si on the Si?111?surface and destroy the flatness of the Si?111?surface.Whether the Si?111?surface is passivated does not weaken the interaction between N and Si.Therefore,in the growth of Si-based gallium nitride,Al atoms must be pre-plated on the surface of Si to prevent nitridation on the Si surface.