Atomic substitution in alloys can efficiently scatter phonons, thereby reducing the thermal conductivity crystalline solids to "alloy limit." Using In0.53Ga0.47As containing ErAs nanoparticles, we demonstrate reduction by almost a factor of 2 below alloy limit and corresponding increase thermoelectric figure merit 2. A theoretical model suggests that while point defects short-wavelength nanoparticles provide an additional scattering mechanism for mid-to-long-wavelength phonons.

We demonstrate THz metamaterials exhibiting either amplitude control, via carrier injection or depletion in the active semiconductor substrate frequency photoexcitation of carriers into semiconducting materials incorporated sub-wavelength metamaterial structure.

In this paper, we explore electron filtering as a technique to increase the Seebeck coefficient and thermoelectric power factor of heterostructured materials over that bulk. We present theoretical model in which can be increased an ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$-based composite material. Experimental measurements cross-plane are presented confirm importance decouple electrical conductivity factor.

We demonstrate optical switching of electrically resonant terahertz planar metamaterials fabricated on ErAs/GaAs nanoisland superlattice substrates. Photoexcited charge carriers in the shunt capacitive regions constituent elements, thereby modulating response metamaterials. A recovery time 20 ps results from fast carrier recombination

The 3ω technique and time-domain thermoreflectance (TDTR) are two experimental methods capable of measuring the cross-plane thermal conductivity thin films. We compare measured by method TDTR on epitaxial (In0.52Al0.48)x(In0.53Ga0.47)1−xAs alloy layers with embedded ErAs nanoparticles. Thermal conductivities at low modulation frequencies (∼1 MHz) typically in good agreement method. discuss accuracy limitations both provide guidelines for estimating uncertainties each approach.

We demonstrate fast electrical modulation of freely propagating terahertz waves at room temperature using hybrid metamaterial devices. The devices are planar metamaterials fabricated on doped semiconductor epitaxial layers, which form metamaterial—Schottky diode structures. With an applied ac voltage bias, we show radiation inferred frequencies over 2MHz. speed is limited by the device depletion capacitance may be reduced for even faster operation.

The effect of nanoparticles on the thermoelectric power factor is investigated using relaxation time approximation. partial-wave technique used for calculating nanoparticle scattering cross section exactly. We validate our model by comparing its results to experimental data obtained ErAs:InGaAlAs samples. use theory maximize with respect and electron concentrations as well barrier height. found that at optimum factor, concentration usually higher in sample nanoparticles, implying Seebeck...

We have grown composite epitaxial materials that consist of semimetallic ErAs nanoparticles embedded in a semiconducting In0.53Ga0.47As matrix both as superlattices and randomly distributed throughout the matrix. The presence these particles increases free electron concentration material while providing scattering centers for phonons. measure concentration, mobility, Seebeck coefficient discuss their potential use thermoelectric power generators.

We demonstrate enhanced terahertz detection using photoconductive antennas based on self-assembled ErAs:GaAs nanoisland superlattices. Three detectors are compared; one each fabricated low-temperature grown GaAs, radiation-damaged silicon-on-sapphire, and an superlattice. The detector shows a strong enhancement in efficiency with respect to incident optical power, though saturation occurs more rapidly. Detected bandwidth signal-to-noise ratios simultaneously maintained or improved.

In0.53Ga0.47BixAs1−x films were grown on InP:Fe substrates by molecular beam epitaxy, with Bi concentrations up to x = 3.60%. content in the epilayers was determined Rutherford backscattering spectroscopy, and channeling measurements show incorporating substitutionally. Unlike previous work, electrical optical data are obtained for all samples. A redshift peak wavelength of about 56 meV/%Bi observed using spectrophotometry. The valence band anti-crossing model is applied, showing...

We report the molecular beam epitaxy growth of Al0.3Ga0.7As∕GaAs multijunction solar cells with epitaxial, semimetallic ErAs nanoparticles at interface tunnel junction. The states provided by these reduce bias required to pass current through junction three orders magnitude, and therefore drastically voltage losses in have measured open-circuit voltages which are 97% sum constituent cells, result nearly double efficiency our cell a conventional

We studied the cross-plane lattice and electronic thermal conductivities of superlattices made InGaAlAs InGaAs films, with latter containing embedded ErAs nanoparticles (denoted as ErAs:InGaAs). Measurements total conductivity at four doping levels a theoretical analysis were used to estimate superlattices. The results show that have marginal dependence on levels. This suggests there is lateral conservation momentum during thermionic emission in superlattices, which limits fraction available...

Rare-earth impurities in III–V semiconductors are known to self-assemble into semimetallic nanoparticles which have been shown reduce lattice thermal conductivity without harming electronic properties. Here, we show that adjusting the band alignment between ErAs and In0.53Ga0.47−XAlXAs allows energy-dependent scattering of carriers can be used increase thermoelectric power factor. Films various Al concentrations were grown by molecular beam epitaxy, properties characterized. We observe...

Thermal conductivity of a crystalline solid at high temperature is dominated by the Umklapp process because number frequency phonons increases with temperature. It challenging to reduce thermal solids although it widely known that, increasing atomic defect concentration, can be reduced low By concentration ErAs nanoparticles in In 0.53Ga 0.47As up 6 atom %, we demonstrate reduction almost factor 3 below that A theoretical model suggests mean free path suppressed nanoparticle concentration.

Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases the bandgap, Eg, spin-orbit splitting, ΔSO, respectively. The possibility achieving ΔSO > Eg a reduced temperature (T) dependence for are significant suppressing recombination losses improving performance mid-infrared photonic devices. We measure Eg(x, T) (x, In0.53Ga0.47BixAs1−x/InP samples 0 ≤ x 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence...

The capability of magnons to hybridize and strongly couple with diverse excitations offers a promising avenue for realizing controlling emergent properties that hold significant potential applications in devices, circuits, information processing. In this Letter, we present recent theoretical experimental developments magnon-based hybrid systems, focusing on the combination magnon excitation an antiferromagnet other excitations, namely, plasmons topological insulator, phonons 2D...

We characterize cross-plane and in-plane Seebeck coefficients for ErAs:InGaAs∕InGaAlAs superlattices with different carrier concentrations using test patterns integrated microheaters. The microheater creates a local temperature difference, the of are determined by combination experimental measurements finite element simulations. compared to significant increase in coefficient over is observed. Differences between decrease as concentration increases, which indicative heterostructure...

Layered semiconductor hyperbolic metamaterials for the mid-infrared are grown by molecular beam epitaxy using a single material system, doped and undoped InAs. The onset wavelength metamaterial behavior can be tuned from 5.8μm to beyond 10μm, while fill factor ranges 0.25 0.75, resulting in designer optical behavior. reflection transmission were studied Fourier transform spectroscopy modeled effective medium theory. We also conducted geometric optics experiment demonstrate negative...

We use optical-pump terahertz (THz)-probe spectroscopy to study carrier dynamics in self-assembled ErAs nanoislands embedded GaAs and deposited a superlattice structure. Measurements are performed at several pump fluences on samples with different periods, enabling determination of the time-dependent conductivity. Subpicosecond capture times obtained, indicating potential these devices as time-domain THz detectors performance comparable low-temperature grown superior control material parameters.

Low dimensional and nanostructured materials have shown great potential to achieve much higher thermoelectric figure of merits than their bulk counterparts. Here, we study the properties superlattices in cross-plane direction using Boltzmann transport equation taking into account multiple minibands. Poisson is solved self-consistently include effect charge transfer band bending profile. The model verified with experimental data Seebeck coefficient for a superlattice structure different...

The Seebeck coefficient of a typical thermoelectric material is calculated without recourse to the relaxation time approximation (RTA). To that end, Boltzmann transport equation solved in one spatial and two k-space coordinates by generalization iterative technique first described Rode. Successive guesses for chemical potential profile are generated until current continuity charge-neutrality bulk device simultaneously satisfied. Both mobility as functions temperature agreement experimentally...

We describe the growth conditions of InxGa1−xBiyAs1−y (lattice-mismatched and matched) on InP substrates by molecular beam epitaxy resulting properties. Due to their anomalously narrow bandgaps presence bismuth, these materials are promising for optoelectronics thermoelectrics. Low temperature moderate As/Bi equivalent pressure ratios beneficial Bi incorporation, in good qualitative agreement with GaBiyAs1−y GaAs. Up 6.75% bismuth is incorporated. High resolution x-ray diffraction reciprocal...