Adsorption and incorporation of silicon at GaN(0001) surfaces

We have studied the adsorption and incorporation of Si at GaN(0001) surfaces employing density-functional theory and scanning tunneling microscopy (STM). Calculating the surface energy of a large number of structures with various Si concentrations and various III–V ratios, we derive a phase diagram showing the energetically most stable surfaces as a function of the Si and N chemical potentials. Based on these results, we identify the surface reconstructions seen in STM, explain the incorporation mechanism of Si on GaN surfaces, and discuss under which conditions Si acts as an antisurfactant.