A. Mazur

The ideal (111), (110) and (100) surfaces of Si, Ge and GaAs; A comparison of their electronic structure

Abstract In this paper we report all surface band structures and some layer densities of states for the ideal (111), (110) and (100) surfaces of Si, Ge and GaAs in comparison. The bulk materials are described by the best available empirical tight-binding Hamiltonians. The surface problem for semi-infinite solids is solved exactly using the Koster-Slater scattering-theoretic technique. The results for the different surfaces and the different materials are compared and characteristic properties stemming from particular surface geometries or varying ionicity are identified unambiguously. The calculations were carried out using first-nearest-neighbour as well as first- and second-nearest-neighbour bulk Hamiltonians. The sensitivity of the surface band structures with respect to the used bulk Hamiltonians is discussed, For some of the eleven different surfaces these are the first surface band structure calculations on the basis of a realistic tight binding bulk description.

Atomic, electronic, and vibronic structure of semiconductor surfaces

A brief review on recent progress in the theory of electronic, structural, and vibronic properties of semiconductor surfaces is presented with particular emphasis on the empirical and selfconsistent scattering theoretical method for semiinfinite systems. The current knowledge of the Si(001) (2×1) surface is discussed in detail. The Ge(001) (2×1) surface, as well as, the clean and the Ge-covered GaAs(110) surfaces are addressed, in addition. In the discussion of the results it is shown, that the scattering theoretical method is an extremely versatile tool for calculating electronic surface properties unambiguously with high spectral resolution concerning energy, wavevector, layer-index and orbital type. Currently used approaches for calculating the total energy, Hellmann-Feynman forces and optimal structure models are summarized. Using the total energy as a starting point, the calculation of atomic force constants and surface phonon spectra is exemplified.

Theory of semiconductor heterojunctions

Abstract A short review of characteristic electronic properties of heterojunction interfaces is given. Band edge discontinuities and interface band structures for lattice-matched junctions are discussed in detail. The examples presented include non-polar and polar junctions as well as overlayer systems. The results of involved calculations are interpreted in terms of simple physically appealing pictures by directly relating the changes in bonds across an interface to the resulting bands in the interface band structure. The meaning of the results for the transport properties of semiconductor heterojunctions is briefly assessed.

Electronic properties of semiconductor surfaces and interfaces: Selected results from green function studies

Abstract In this paper a short overview of characteristic electronic features of semiconductor surfaces and interfaces is given. The examples presented in the discussion of typical surface- and interface-induced physical properties have been evaluated using the tight-binding scattering theoretical method. The systems discussed comprise ideal, relaxed and reconstructed surfaces, adsorbate systems, overlayer systems and heterojunction interfaces.

Photoemission from valence bands of GaAs(001) grown by molecular beam epitaxy

Abstract Angle-resolved photoemission measurements for GaAs(001) prepared by MBE have been carried out using synchroton radiation. Observed bulk features in the spectra can be explained by a direct transition model using free-electron-like final states down to energies as low as 16 eV above the top of the valence bands. Spectral bulk valence band features can be distinguished from surface features by an appropriate choice of photon energies and polar angles. This is demonstrated using calculated valence bands.

Surface phonons of D:Si(111)-(1×1)

Abstract In this short contribution we present and discuss the surface-phonon spectrum and spectral densities for the deuterium-terminated Si(111)−(1 × 1) surface. Our calculations, which are based on a semi-empirical total-energy approach, yield salient adsorbate- and substrate-induced vibrational modes. An analysis of these modes in comparison with previous results for H:Si(111)−(1 × 1) and H:C(111)−(1 × 1) turns out to be very revealing, since D:Si(111)−(1 × 1) proves to be an interesting connecting link between the former two systems as far as surface vibrational properties are concerned. The physical origin of surface modes becomes particularly transparent by relating them to the specifically different mass misfits between respective adsorbate and substrate atoms in the three systems.

Electronic structure of ideal and relaxed InSb(110) surfaces

Abstract We report electronic structure calculations for the ideal and relaxed InSb (110) surfaces which were carried out using the tight binding scattering theoretic method. The bulk material is described by a realistic ETBM Hamiltonian and spin-orbit coupling has been taken into account explicitly. Our results show, that the spin-orbit interaction has only small influence on the surface electronic structure of InSb(110). Our results are discussed in terms of surface band structures, wavevector-resolved layer densities of states and angular-resolved weighted layer densities of states.

Angular-resolved initial state spectra for the relaxed GaAs (110) surface

Abstract We present angular-resolved electronic initial state spectra for the relaxed GaAs (110) surface in direct comparison with experimentally determined electron density curves. The initial state spectra have been calculated using the tight-binding scattering theoretical method for surfaces of semi-infinite solids on the basis of a realistic empirical tight-binding bulk Hamiltonian which was fit to recent bulk photoemission data. The generally accepted surface relaxation model with a tilt angle of 27° has been used in the calculations. Surface- and bulk-derived features are most clearly separated by calculating initial state difference spectra. We find very good general agreement between theory and experiment showing that the calculation of angular-resolved initial state spectra is a useful first step towards a quantitative analysis of ARUPS data from relaxed semiconductor surface.

On the electronic structure of the Si(100)−2×1 surface☆

Abstract We have investigated the electronic structure of the asymmetric dimer model for the Si(100)−2×1 surface using our tight binding scattering theoretical method for semiinfinite crystal on the basis of a realistic bulk Si description. Our results are in good agreement with all available UPS and ARUPS data resolving outstanding discrepancies between previous theoretical results and experiment and they lend strong further support to the asymmetric dimer model proposed by Chadi.

Overlayer systems: Suitable samples for probing heterojunction interface properties

Abstract In this paper we report electronic structure calculations for Ge-(110) GaAs heterostructures. Our results demonstrate that Ge-(110) GaAs overlayer s ystems should be suitable samples for experimental investigations of heterojunction interface properties. We find that a 3 Ge-(110) GaAs overlayer system shows all bound interface states characteristic for the (110) Ge-GaAs heterojunction . Interface-induced resonances or semiresonances occur strongly enhanced in the overlayer system as compared to the true heterojunction. The wavevector-resolved weighted layer density of states at the Brillouin zone center, for example, shows a salient structure of interface-induced density peaks which should readily be accessible to normal emission ARUPS experiments.