Temperature-dependent Hall-effect measurements were carried out both in dark and ambient light on Si-doped ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, measured Hall carrier densities (different from actual electron near direct-indirect transition) show an exponential dependence temperature. A shallow donor (\ensuremath{\le}15 meV) tied to $\ensuremath{\Gamma}$ band a deep level $L$...

We present the results of a study energy spectrum ground state and low-lying excited states for shallow donors in quantum well structures consisting single slab GaAs sandwiched between two semi-infinite layers ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$. The effect position impurity atom within central is investigated different thicknesses alloy compositions. Two limiting cases are presented: one which located at center (on-center impurity), other edge (on-edge impurity)....

Two-dimensional metallic broadband absorbers on a SiO(2)/Ag/Si substrate were experimentally studied. The absorptivity of such structure can be increased by tailoring the ratio disk size to unit cell area. exhibits localized surface plasmon polariton (LSPP) mode for both TE and TM polarizations. A thermal emitter realized because LSPP is independent periodicities. By manipulating ratios sizes, high-performance, wide-angle, polarization-independent dual band absorber was achieved. results...

We present theoretical studies of the electronic and optical properties free-standing Si quantum wires which exist in porous Si. use a second-neighbor empirical tight-binding model includes d orbitals spin-orbit interaction. The excitonic effects are included within effective-mass approximation. found that for narrow with widths around 8 A\r{}, averaged exciton oscillator strength is comparable to bulk GaAs. However, average decreases dramatically (faster than 1/${\mathit{L}}^{5}$) as...

Much understanding of the electronic and optical properties a semiconductor superlattice can be obtained by relating wave functions band structure to those two bulk semiconductors from which it is constructed. In this paper, relationship studied within framework empirical tight-binding model, solved using reduced Hamiltonian technique. The are described as linear combinations Bloch with complex vectors, twenty (including spin) for each constituent materials. Bloch-function composition...

Optical properties of GaAs-${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Al}}_{\mathrm{x}}$As and InAs-GaSb superlattices are studied within the framework tight-binding approximation. The momentum matrix elements between orbitals related to those Brillouin-zone-center Bloch states computed by a full-zone k\ensuremath{\rightarrow}\ensuremath{\cdot}p\ensuremath{\rightarrow} theory. optical transitions from several valence subbands conduction calculated as functions well width...

Spin-polarized photoemission experiments on expitaxial Ag overlayers Fe(001) have shown that a minority-spin surface state of the bare substrate evolves into an interface state, moves to higher energies, and crosses Fermi level ${\mathit{E}}_{\mathit{F}}$ between 3 4 monolayers. Application phase accumulation model shows this is quantum-well (QW) characterized by quantum number \ensuremath{\nu}=1, where \ensuremath{\nu}=m-n, n m are wave-function nodes layers, respectively. Higher members QW...

We have experimentally determined the absolute optical-absorption coefficients and exciton oscillator strengths in AlGaAs-GaAs superlattices at liquid-helium temperatures. find that although magnitude of band-to-band absorption coefficient is essentially independent quantum-well width, due to greatly enhanced as well width becomes smaller. The energies are compared theoretical calculations shown be very good agreement. strength per unit volume proportional 1/${L}^{2}$ narrow wells. effects...

Highly-oriented indium tin oxide nanocolumns are prepared by glancing-angle deposition with nitrogen. The tapered column profiles, which function as a graded-refractive-index layer, offer superior antireflective characteristics. nanostructured material serves the conductive layer for GaAs solar cells, demonstrating viable efficiency-boosting strategy next-generation photovoltaics.

In this paper we study the phonon dispersion in superlattices consisting of alternating layers semiconductors. First parameters adiabatic bond-charge model are obtained. Then it is shown that an excellent approximation to curves bulk semiconductors can be obtained first by a zeroth-order calculation which includes only short-range forces and Coulomb interactions between ions bond charges same neighboring layers, then first-order perturbation include effect remaining forces. Thus possible...

A general method for calculating the complex band structures of solids is presented. This adaptable to pseudopotential, full-zone $\stackrel{\ensuremath{\rightarrow}}{k}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{p}$, and tight-binding formalisms. The basic idea express total Hamiltonian bulk material as a polynomial in simple analytic function wave vector perpendicular given plane. companion matrix associated with this constructed, then diagonalized....

A well-resolved split peak at the n=2 heavy-hole exciton transition observed low temperatures in excitation spectra is characteristic of \ensuremath{\approxeq}100-A\r{}-wide square GaAs quantum wells high quality. Theoretical calculations using a multiband effective-mass approach demonstrate that lower-energy component arises from transitions involving n=1 light hole and electron. This strong transition, which normally parity forbidden for symmetric wells, becomes allowed due to valence-band...

We present a variational calculation of acceptor binding energies in GaAs-${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ quantum well. The includes the coupling top four valence bands both materials multiband effective-mass approximation. Because quantum-well potential reduces bulk symmetry, ${\ensuremath{\Gamma}}_{8}$ ground state splits into ${\ensuremath{\Gamma}}_{6}$ and ${\ensuremath{\Gamma}}_{7}$ states. ground-state symmetries have been calculated for three barrier...

Binding energies and oscillator strengths of ground-state Wannier excitons in GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum wells are studied by a multiband effective-mass method. The present calculation incorporates valence-band nonparabolicity resulting from the hybridization heavy light holes. variation exciton binding energy strength as function GaAs well width aluminum mole fraction...

The electrical conductance, thermal power and figure of merit (ZT) semiconductor quantum dots (QDs) embedded into an insulator matrix connected with metallic electrodes are theoretically investigated in the Coulomb blockade regime. multilevel Anderson model is used to simulate multiple QDs junction system. charge heat currents sequential tunneling process calculated by Keldysh Green function technique. In linear response regime ZT values still very impressive small rates case, although...

The electronic structure of semiconductor superlattices is analyzed in terms complex bulk band structures. details the bands and matching conditions at interfaces are found to be crucial energy ranges experimental interest. limits applicability Kronig-Penney two-band models shown.

We observe a set of three replica luminescent peaks at ~21.4 meV below the dark exciton, negative and positive trions (or exciton-polarons) in monolayer WSe2. The redshift energy matches zone-center E"-mode optical phonons. phonon replicas exhibit parallel gate dependence same g-factors as excitonic states, but follow valley selection rules bright states. While states out-of-plane transition dipole valley-independent linearly polarized emission in-plane directions, their valley-dependent...

Excitons and trions (or exciton-polarons) in transition metal dichalcogenides (TMDs) are known to decay predominantly through intravalley transitions. Electron-hole recombination across different valleys can also play a significant role the excitonic dynamics, but intervalley transitions rarely observed monolayer TMDs, because they violate conservation of momentum. Here we reveal dark excitons more than one path WSe$_2$. We observe excitons, which recombine by assistance defect scattering or...

Exciton polaron is a hypothetical many-body quasiparticle that involves an exciton dressed with polarized electron-hole cloud in the Fermi sea. It has been evoked to explain excitonic spectra of charged monolayer transition metal dichalcogenides, but studies were limited ground state. Here we measure reflection and photoluminescence MoSe2 WSe2 gating devices encapsulated by boron nitride. We observe gate-tunable polarons associated 1 s-3 s Rydberg states. The excited exhibit comparable...

Spin polarized photoemission is used to examine the spin polarization of quantum well states observed in copper films grown on a fcc Co(001) substrate. The are predominantly carry minority and this shown through comparison with calculation reflect preferential hybridization interface. also provides evidence that experiments not only sp derived but more localized d bands.

Saturation behavior of intersubband optical transitions in p-type semiconductor quantum wells is examined theoretically with the multiband effective-mass model. Carrier-phonon scatterings are taken into account within deformation-potential approximation. Deviation hole distribution from thermal equilibrium due to pumping calculated by solving coupled rate equations. Pump-and-probe absorption spectra also studied, and possible applications for light-by-light modulation discussed.

A systematic study of the electronic and optical properties modulation-doped GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum wells is undertaken. We consider cases in which ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As barriers are doped either n or p type GaAs filled with a gas free carriers. The band structure, exciton binding energy, oscillator strength, interband absorption studied as functions well...

We have used the variational method to calculate acceptor binding energies in GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum wells with and without application of electric, magnetic, uniaxial stress fields. The calculation includes coupling top four valence bands both materials multiband effective-mass approximation. To ensure convergence calculation, a large number basis functions which are made up s-like, p-like, or d-like spatial states...

A theoretical calculation of the optical properties GaAs-Ga1−xAlxAs superlattices is presented. The includes detailed atomic nature superlattice electronic states in a realistic tight-binding model. It found that mixture bulk heavy hole and light wave function substantially affects properties.