We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

TiO2 nanotubes: synthesis and applications.

The surface and materials science of tin oxide

Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process

This review provides numerical and graphical information about many (but by no means all) of the physical and electronic properties of GaAs that are useful to those engaged in experimental research and development on this material. The emphasis is on properties of GaAs itself, and the host of effects associated with the presence of specific impurities and defects is excluded from coverage. The geometry of the sphalerite lattice and of the first Brillouin zone of reciprocal space are used to pave the way for material concerning elastic moduli, speeds of sound, and phonon dispersion curves. A section on thermal properties includes material on the phase diagram and liquidus curve, thermal expansion coefficient as a function of temperature, specific heat and equivalent Debye temperature behavior, and thermal conduction. The discussion of optical properties focusses on dispersion of the dielectric constant from low frequencies [κ0(300)=12.85] through the reststrahlen range to the intrinsic edge, and on the ass...

Semiconducting and other major properties of gallium arsenide

The polarization-dependent absorption spectra and wavelength-modulated absorption spectra of Ti${\mathrm{O}}_{2}$ have been measured under very-high-resolution conditions between 1.6 and 300\ifmmode^\circ\else\textdegree\fi{}K. For the first time the fine structure of the fundan ental absorption edge is resolved and a detailed investigation is presented. We find an indirect allowed transition ${\ensuremath{\Sigma}}_{4v}\ensuremath{\rightarrow}{\ensuremath{\Gamma}}_{1c}$, characterized by a small doublet (3.061-3.065 eV at 1.6\ifmmode^\circ\else\textdegree\fi{}K) which constitutes the fundamental transition in polarization $\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}$ parallel to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{C}}$. In polarization perpendicular to $\stackrel{\ensuremath{\rightarrow}}{\mathrm{C}}$, we find the same indirect transition plus a new forbidden direct transition ${\ensuremath{\Gamma}}_{3v}\ensuremath{\rightarrow}{\ensuremath{\Gamma}}_{1c}$ which appears at slightly lower energy (3.031 eV at 1.6\ifmmode^\circ\else\textdegree\fi{}K). The fine structure of the forbidden exciton is resolved and the ionization energy is 4 meV.

Fine structure in the intrinsic absorption edge of Ti O 2

We present a very simple method for calculating exciton binding energies in quantum-confined semiconductor structures. The aim of the model calculation, which is developed in the framework of the fractional-dimensional space, is not to compete with the very advanced ones already proposed, but, on the contrary, to avoid tedious and expensive calculations, to obtain, with good accuracy, the exciton binding energy in most of the confined structures where the exciton can be associated with a specific pair of electron and hole subbands. Our main result is an analytical expression for the exciton binding energy, free of any adjustable parameter. Furthermore, in the cases where the 1s and 2s transition energies can be experimentally measured, the method permits one to obtain the exciton binding energy without any hypothesis or calculation.

Simple analytical method for calculating exciton binding energies in semiconductor quantum wells.

Time-resolvedphotoluminescence (PL), at T=8 K, is used to study a graded-width InGaN/GaN quantum well. Across the sample, the well width continuously varies from ∼5.5 to 2.0 nm corresponding to PL peak energies varying between 2.0 and 2.9 eV and to PL decay rates covering four orders of magnitude. The plot of decay times versus PL energies is very well fitted by a calculation of the electron–hole recombination probability versus well width. The only fitting parameter is the electric field in the well, which we find equal to 2.45±0.25 MV/cm, in excellent agreement with experimental Stokes shifts for this type of samples.

High internal electric field in a graded-width InGaN/GaN quantum well: Accurate determination by time-resolved photoluminescence spectroscopy

We report an investigation of the fundamental absorption edge of InSe under high-resolution conditions. We resolve three components of the direct exciton series and obtain an effective Rydberg energy of 14.5 meV. From this value an effective mass ($m=0.10 {m}_{0}$) of electrons in the $\ensuremath{\Gamma}$ minimum of the conduction band is obtained. We analyze the absorption coefficient with a three-dimensional model and find a remarkable agreement. We deduce an interband matrix element in polarization $\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ensuremath{\perp}\stackrel{\ensuremath{\rightarrow}}{\mathrm{C}}:{P}_{\ensuremath{\perp}}^{2}=0.6$ eV. Next we investigate the temperature dependence of the fundamental absorption edge. We find a strong interaction with a 14-meV phonon which accounts for (i) the shift of the band-gap energy in the full temperature range between liquid-helium temperature and 300\ifmmode^\circ\else\textdegree\fi{}K and (ii) the temperature dependence of the broadening parameter (exciton lifetime). A simple analytical expression is obtained which accounts for the temperature dependence of the band gap and the $n=1$ exciton structure. Last, we deduce the electron-phonon coupling constant.

Excitonic absorption edge of indium selenide

Very strong coefficients for spontaneous and piezoelectric polarizations have recently been predicted for III-V nitride semiconductors with natural wurtzite symmetry. Such polarizations influence significantly the mechanisms of radiative emissions in quantum-confinement heterostructures based on these materials. The photoluminescence decay time of excitons is used as a probe of internal electric fields in GaN-(Ga, Al)N quantum wells in various configurations of strain, well widths, and barrier widths. The measured decays are not only controlled by radiative lifetimes, which depend on the fields inside GaN wells but also on the nonradiative escape of carriers through Ga1 - xAlyN barriers, which depends on their widths and on the electric field in these layers. It is shown in particular that the magnitude of the held in the wells is not a simple function of the strain of these layers via the only piezoelectric effect, but rather the result of the interplay of spontaneous and piezoelectric polarizations in both well and barrier materials. [S0163-1829(99)02923-9].

Henry Mathieu

Papers

Fine structure in the intrinsic absorption edge of Ti O 2

Simple analytical method for calculating exciton binding energies in semiconductor quantum wells.

High internal electric field in a graded-width InGaN/GaN quantum well: Accurate determination by time-resolved photoluminescence spectroscopy

Excitonic absorption edge of indium selenide

Time-resolved photoluminescence as a probe of internal electric fields in GaN-(GaAl)N quantum wells