The electronic band structures of silicon and the zinc-blende-type III-N semiconductor compounds BN, AlN, GaN, and InN are calculated by using the self-consistent full potential linear augmented plane wave method within the local-density functional approximation. Lattice constant, bulk modulus, and cohesive energy are obtained from full relativistic total-energy calculations for Si and for the nitrides. Band structures and total density of states (DOS) are presented. The role played by relativistic effects on the bulk band structures and DOS is discussed. In order to provide important band structure-derived properties, such as effective masses and Luttinger parameters, the ab initio band structure results are linked with effective-mass theory. Electron, heavy-, light-, and split-off-hole effective masses, as well as spin-orbit splitting energies are extracted from the band-structure calculations. By using the Luttinger-Kohn $6\times 6$ effective-mass Hamiltonian we derive the corresponding Luttinger parameters for the materials. A comparison with other available theoretical results and experimental data is made.

We employ density-functional theory (DFT) within the local-density approximation (LDA) and generalized-gradient approximation (GGA) to study structural and electronic properties of clean $\mathrm{GaN}\left(0001\right)$ surfaces. The pseudopotential method is used to investigate surfaces with $(1\times 1)$, $(2\times 2)$, and $(\sqrt{3}\times \sqrt{3})R30°$ reconstructions. We also report calculations for the ${\mathrm{N}}_2$ molecule and for the bulk phases of Ga and $\mathrm{GaN}$. We find that GGA give better results than LDA for the cohesive energies, but not for the structural properties. Bulk band structures are found to be very similar for both exchange-correlation potentials. Examining the clean $\mathrm{GaN}\left(0001\right)$ surfaces we conclude that both potentials give very similar relaxations and an almost identical dispersion for the surface states. We also report results for ionization energies, electron affinities, and work function for the $\mathrm{GaN}\left(0001\right)$ surfaces. As a general trend the ionization energy decreases monotonically with the increasing of the Ga-coverage.

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.

We report in detail the results of our first-principles investigations of Si adsorption on GaN(0001) surfaces which were briefly presented in an earlier publication [Appl. Phys. Lett. 80, 2008 (2002)]. We employ density-functional theory within the local-density approximation to investigate Si adsorption on GaN(0001) surfaces with $(1\times 1)$, $(2\times 2)$, and $(\sqrt{3}\times \sqrt{3})R30°$ reconstructions. We find that adsorption at subsurface sites is energetically favorable compared to adsorption on the top layers. In particular, we find that under Ga-rich conditions a Ga bilayer is formed on the top of a Ga-terminated surface with Si incorporated underneath. Under such conditions Si does not affect the GaN surface morphology. Under both N-rich and Si-rich conditions, an N-terminated structure with Si in the second layer is preferred, leading to rough surfaces.