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

The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles:  gold nanospheres, silica−gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (∼40 nm)...

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Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15 nm layer of CH3NH3PbI(3-x)Cl(x) perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9'-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2 W sr(-1) m(-2) at a current density of 363 mA cm(-2), with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364 cd m(-2) at a current density of 123 mA cm(-2), giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.

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Bright light-emitting diodes based on organometal halide perovskite

First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...

First-principles calculations for defects and impurities: Applications to III-nitrides

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

Recent advances in fabrication technologies for the semiconducting nitrides of the group III elements have led to commercially available, high-efficiency solid-state devices that emit green and blue light Light-emitting diodes based on these materials should find applications in flat-panel displays, and blue and ultraviolet laser diodes promise high-density optical data storage and high-resolution printing

Nitride-based semiconductors for blue and green light-emitting devices

The activation kinetics of acceptors was investigated for heteroepitaxial layers of GaN, doped with Mg. After growth, the samples were exposed to isochronal rapid thermal anneals in the temperature range from 500 to 775 °C. The samples were studied by variable temperature Hall effect measurements and photoluminescence (PL) spectroscopy in the as‐grown condition and after each temperature step. The thermal treatment reduced the resistivity by six orders of magnitude and the p‐type conductivity was found to be dominated by an acceptor with an activation energy of ∼170 meV. This acceptor is attributed to Mg atoms substituting for Ga in the GaN lattice and the activation process is consistent with dissociation of electrically inactive Mg–H complexes. It is shown that the appearance of a blue emission band in the PL spectrum of Mg‐doped GaN does not directly correlate with the increase in p‐type conductivity.

Activation of acceptors in Mg-doped GaN grown by metalorganic chemical vapor deposition

The spatial dependence of the luminescence intensities at the band edge (364 nm) and at the ‘‘yellow’’ defect‐band (centered at 560 nm) regions for epitaxial GaN films have been studied using cathodoluminescence microscopy at room temperature. The films were grown by metalorganic chemical vapor deposition on (0001) sapphire substrates and were not intentionally doped. Significant nonuniformities in the band‐to‐band and in the yellow band emissions were observed. Yellow luminescence in small crystallites appears to originate from extended defects inside the grains and at low‐angle grain boundaries. The size of band‐to‐band emission sites correlates with low‐angle grain sizes observed by transmission electron microscopy.

Spatial distribution of the luminescence in GaN thin films

Indium–gallium nitride (InGaN) multiple-quantum-well (MQW) light-emitting diode (LED) membranes, prefabricated on sapphire growth substrates, were created using pulsed-excimer laser processing. The thin-film InGaN MQW LED structures, grown on sapphire substrates, were first bonded onto a Si support substrate with an ethyl cyanoacrylate-based adhesive. A single 600 mJ/cm2, 38 ns KrF (248 nm) excimer laser pulse was directed through the transparent sapphire, followed by a low-temperature heat treatment to remove the substrate. Free-standing InGaN LED membranes were then fabricated by immersing the InGaN LED/adhesive/Si structure in acetone to release the device from the supporting Si substrate. The current–voltage characteristics and room-temperature emission spectrum of the LEDs before and after laser lift-off were unchanged.

Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off

There is a great interest in wide-bandgap semiconductor devices and most recently in monolithic GaN structures for power electronics applications. In this paper, vertical p-n diodes fabricated on pseudobulk low defect density ( $10^{4}$ – $10^{6}$ cm $^{-2}$ ) GaN substrates are discussed. Homoepitaxial low-pressure metal organic chemical vapor deposition growth of GaN on its native substrate and being able to control and balance the n-type Si doping with background C impurity has allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 $\mu $ m and net carrier electron concentrations of $4\times 10^{15}$ to $2.5\times 10^{16}$ cm $^{-3}$ . This parameter range is suitable for applications requiring breakdown voltages (BVs) of 600 V–4 kV with a proper edge termination strategy. Measured devices demonstrate near power device figure of merit, that is, differential specific on-resistance ( $R_{{{\textrm {sp}}}}$ ) of 2 m $\Omega $ cm $^{2}$ for a BV of 2.6 kV and 2.95 m $\Omega $ cm $^{2}$ for a 3.7-kV device, respectively. The improvement in the substrate quality over the last few years has resulted in the fabrication of diodes with areas as large as 16 mm $^{2}$ , with BVs exceeding 700 V and pulsed (100 $\mu $ s) currents of 400 A. The structures fabricated are utilized to study in detail the temperature dependency of $I$ – $V$ characteristics, impact ionization and avalanche characteristics, and extract (estimate) modeling parameters such as electron mobility in the GaN $c$ -direction (vertical) and hole minority carrier lifetimes. Some insight into device reliability is also provided.

David P. Bour

Papers

Nitride-based semiconductors for blue and green light-emitting devices

Activation of acceptors in Mg-doped GaN grown by metalorganic chemical vapor deposition

Spatial distribution of the luminescence in GaN thin films

Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off

Vertical Power p-n Diodes Based on Bulk GaN