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Spatially resolved x-ray fluorescence (XRF) based analysis employing incident beam sizes in the low micrometer range (μ XRF) is widely used to study lateral composition changes of various types of microstructured samples. However, up to now the quantitative analysis of such experimental datasets could only be realized employing adequate calibration or reference specimen. In this work, we extent the applicability of the so-called reference-free XRF approach to enable reference-free μ XRF analysis. Here, no calibration specimen are needed in order to derive a quantitative and position sensitive composition of the sample of interest. The necessary instrumental steps to realize reference-free μ XRF are explained and a validation of ref.-free μ XRF against ref.-free standard XRF is performed employing laterally homogeneous samples. Finally, an application example from semiconductor research is shown, where the lateral sample features require the usage of ref.-free μ XRF for quantitative analysis. [ABSTRACT FROM AUTHOR]

The degradation of organic pollutants by transition metal activated peroxymonosulfate (PMS) has important application value in the field of advanced oxidation. MnO2/SiC composite catalyst was prepared by hydrothermal method on the surface of silicon carbide (SiC), which was used to activate PMS to degrade and remove methylene blue (MB) from water. The results show that MnO2 is uniformly attached to the surface of SiC in the form of particles, and the removal rate of MB by MnO2/SiC-PMS system reaches 99% within 40 min. The MnO2/SiC-PMS system can achieve high degradation efficiency of MB over a wide pH range (5.0~9.0), while 5 mmol/L Cl- and NO3- had no significant effect on the MnO2/SiC-PMS system. Phosphate and bicarbonate have quenching effect on oxidative free radicals, leading to a decrease in the degradation efficiency of MB in the MnO2/SiC PMS system. The results of free radical quenching experiments indicate that plays a major role in the MnO2/SiC-PMS system. In addition, MnO2/SiC has good recyclability. [ABSTRACT FROM AUTHOR]

The design of semiconductor-based heterojunction structures can be turned useful to raise the efficiency of nuclear micro-batteries. In this study, we have investigated a micro-power alphavoltaic battery by using a lab-made software. The nuclear battery consists of an In0.49Ga0.51P/GaAs heterostructure irradiated by americium-241 (Am241) alpha particles with an average kinetic energy of 5.485 MeV. The alphavoltaic battery exhibits an overall active area of 1 cm². Based on a comprehensive analytical model, the device current density-voltage J(V) and output electric power P(V) characteristics are simulated extracting the energy conversion efficiency. The model takes into account the reflection of the incident alpha particles, the ohmic losses, the effect of the boundary between the two layers, and the depletion region borders. Different values of the radioisotope apparent activity density, the emitter and base dopant concentrations, and the surface recombination velocities in both the front and back layers are considered during the simulations to optimize the battery performance. The present study reports that by irradiating by a 2.4 mCi/cm² Am241 source, the obtained energy conversion efficiency of the battery can reach 10.31% with a maximum output power density of 16.07 μW/cm². Therefore, In0.49Ga0.51P/GaAs heterostructure coupled with Am241 seems a promising design for long- term energy supply in harsh environments. [ABSTRACT FROM AUTHOR]

Reliable and controllable growth of two-dimensional (2D) hexagonal boron nitride (h-BN) is essential for its wide range of applications. Substrate engineering is one of the critical factors that influence the growth of the epitaxial h-BN films. Here, we report the growth of monolayer h-BN on Ni (111) substrates incorporated with oxygen atoms via molecular beam epitaxy. It was found that the increase of incorporated oxygen concentration in the Ni substrate through a pretreatment process prior to the h-BN growth step would have an adverse effect on the morphology and growth rate of 2D h-BN. Under the same growth condition, h-BN monolayer coverage decreases exponentially as the amount of oxygen incorporated into Ni (111) increases. Density functional theory calculations and climbing image nudged elastic band (CI-NEB) method reveal that the substitutional oxygen atoms can increase the diffusion energy barrier of B and N atoms on Ni (111) thereby inhibiting the growth of h-BN films. As-grown large-area h-BN monolayer films and fabricated Al/h-BN/Ni (MIM) nanodevices were comprehensively characterized to evaluate the structural, optical and electrical properties of high-quality monolayers. Direct tunneling mechanism and high breakdown strength of ∼11.2 MV cm−1 are demonstrated for the h-BN monolayers grown on oxygen-incorporated Ni (111) substrates, indicating that these films have high quality. This study provides a unique example that heterogeneous catalysis principles can be applied to the epitaxy of 2D crystals in solid state field. Similar strategies can be used to grow other 2D crystalline materials, and are expected to facilitate the development of next generation devices based on 2D crystals. [ABSTRACT FROM AUTHOR]

We present the study of the SiGe quantum ring (QR) modeled by an anharmonic axially symmetric potential with a centrifugal core in the effective mass approximation. We show how the femtosecond laser pulses (FLPs) can be used efficiently for controlling the induced current and magnetic field. We have compared the strength of induced currents and magnetic fields with and without pulsed laser which shows a substantial change. The spin-orbit interaction (SOI) and Zeeman energy show a massive impact on the generation and enhancement of these induced current and magnetic fields. These induced currents and magnetic fields have many applications in interdisciplinary areas. We have shown that the SOI presence with the FLP fields while competing with the confinement strength lowers the strength of the induced current and field. [ABSTRACT FROM AUTHOR]

Comparison of optical power, external quantum efficiency in InGaN/GaN UV LEDs at room temperature and liquid nitrogen temperature is carried out. The spectral densities of the current low-frequency noise have been investigated. The mechanisms of carrier transport, the formation of low-frequency noise, and the dependences of the rates of radiative and nonradiative recombination at room and nitrogen temperatures are considered. [ABSTRACT FROM AUTHOR]

High-density integration of ferroelectric field-effect transistors (FeFETs) is hindered by factors such as interfacial states, short-channel effects, and ferroelectricity degradation in ultrathin films. Accordingly, the introduction of two-dimensional (2D) materials could effectively solve these problems. However, most current studies focus on the replacement of Si-based channels with 2D channels. Little progress has been made in addressing issues caused by bulk-phase ferroelectric gate layers, such as the unavoidable rough interfaces and the fading of ferroelectricity in ultrathin films. Herein, the 2D ferroelectric material In2Se3 is introduced as the gate dielectric. Combined with 2D insulating h-BN and 2D channel MoS2, an all-van der Waals (vdW) stacking FeFET is fabricated to provide a straight solution for the abovementioned issues. First, the robust ferroelectric phase of In2 Se3 is verified in an ultrathin film case and a high-temperature case, which is outstanding among recently reported 2D ferroelectrics. Second, device-level out-of-plane ferroelectric polarization switching is achieved in the cross-structure device. Based on these results, In2 Se3 is adopted as the ferroelectric gate dielectric to fabricate all-vdW stacking FeFETs. The subsequent transistor performance measurement on the fabricated FeFETs indicates that the ferroelectric polarization of the In2 Se3 layer plays a dominating role in forming a counterclockwise hysteresis loop. Further pulse response measurements manifest the feasibility of nonvolatile channel conductance tuning of these devices with a proper pulse design. Our findings suggest that In2Se3 is a suitable 2D ferroelectric gate material and that all-vdW stacking FeFETs based on 2D ferroelectrics are promising in the application of high-density memory. [ABSTRACT FROM AUTHOR]

Effect of irradiation with 0.9 MeV electrons on the parameters of 4H-SiC Schottky diodes with a limiting blocking voltage Ub = 600 and 1700 V was studied for the first time in the range of operating temperatures Ti (23 and 175°C). The range of fluences Φ was 1 × 1016–2 × 1016 cm–2 for devices with Ub = 600 V and 5 × 1015–1.5 × 1016 cm–2 for devices with Ub = 1700 V. Irradiation at room temperature increases significantly the differential resistance of the base of the diodes. Irradiation with the same doses at Ti = 175°C—i.e. at limiting operating temperature of devices, does not affect practically the parameters of current–voltage characteristics. Nevertheless, the DLTS spectra demonstrate a significant increase in the concentration of deep levels in the upper half of the band gap not only after irradiation at room temperature, but also after irradiation at Ti = 175°C. [ABSTRACT FROM AUTHOR]

The effect of proton irradiation (proton energy 15 MeV) on the parameters of high-voltage 4H-SiC integrated Schottky diodes (JBS) was studied for the first time in the operating temperature range Ti (23 and 175°C). The blocking voltage of the diodes under study, Ub, was 600 and 1700 V. For devices with Ub = 600 V, the fluence range was 5 × 1013–1 × 1014 cm–2; for devices with Ub = 1700 V, the fluence range was 3 × 1013–6 × 1013 cm–2. An increase in the irradiation temperature leads to a noticeable decrease in the effect of irradiation on the current–voltage characteristics of the diodes. The effect of annealing on the current-voltage characteristics of irradiated devices is studied. [ABSTRACT FROM AUTHOR]

Film structures based on Si1–xGex (0 < x < 1) solid solutions are currently obtained by chemical-vapor-deposition methods. For device application of the obtained structures, it is necessary to know the electrical properties of the material synthesized under different conditions. In this work, we carry out galvanomagnetic studies of the electrical conductivity in porous and solid Si1–xGex films, as well as the concentration and mobility of the majority charge carriers in them at a temperature of 30–300 K. It is shown that, as in pure silicon and germanium of comparable porosity, the electrical conductivity in the studied samples can be considered as in a medium with voids. It is established that the type of majority charge carriers in the alloy is determined by the type of silicon substrate used. This is practically important for creating both arms of a thermoelectric converter, which makes the method for producing Si1–xGex(0 < x < 1) alloy promising for device applications, in particular in thermoelectric converters and lithium-ion batteries. [ABSTRACT FROM AUTHOR]

NH- ÎĽ LED, namely a micro light-emitting diode structure with nano-holes dug all the way through the active region, is designed to make silver nanoparticles in extremely close contact with the quantum wells for improving the coupling between the localized surface plasmon and the quantum wells (LSP-QWs coupling) and thus enhancing the optical properties of the ÎĽ LED. The experimental results show that, thanks to this deep nanohole structure, the LSP-QWs coupling can be realized effectively, which ultimately increases the optical performance of the ÎĽ LED. The internal quantum efficiency of the NH- ÎĽ LED filled with silver nanoparticles is increased by 12%, and the final optical output power is also enhanced. We have further carried out a comparison study which measures the transient lifetime of two different types of ÎĽ LEDs, and the results provide convincing evidence for the existence of the ultra close range LSP-QWs coupling effect. [ABSTRACT FROM AUTHOR]

In this article, we study 1 / f γ , γ ≈ 1 electrical noise in amorphous phase-change materials. Given the relevance of noise in recent applications, it is necessary to gain a deeper perspective on its nature in phase-change semiconductors, a promising class of materials. Electron conduction is envisaged in terms of an envelope function and a field-dependent Bloch wave function; the electron transport across the structure is modeled as driven phase oscillators under a weak field and obeys a Kuramoto-type equation. Its solutions naturally divide into a phase-synchronized group and phase-desynchronized oscillators. The former is comprised by long-lived pairs or aggregates and are responsible for 1 / f , γ = 1 noise. We identify the dividing frequency between γ = 1 noise and γ ≠ 1 noise. The phase-desynchronized carriers generate γ ≠ 1 noise and are single carriers, not aggregates, and are short-lived. We apply our analysis to recent experiments. [ABSTRACT FROM AUTHOR]

The excrescent electromagnetic (EM) radiation exposure in the air threatens human health and electronic equipment due to the abuse of EM waves in wireless telecommunication technology and electronic applications. Consequently, electromagnetic interference (EMI) shielding materials are provided to solve the EM waves pollution problem. In particular, the appearance of one-dimensional (1D) metallic, magnetic, and dielectric nanofillers will extremely reduce the density of EMI composite and enhance EMI protection performance because they can easily assemble to form complete two-dimensional (2D) or three-dimensional (3D) EMI network based on their high aspect ratio, large specific surface area, and additional attenuated sites. This review focuses on the EMI shielding composites with 1D metallic, magnetic, and dielectric nanofillers, which could be constructed in the final form of membrane- or aerogel/sponge-like shielding materials. According to the structural features, 1D metallic, magnetic, and dielectric nanofillers are classified into nanowires, nanorods, nanospindles, nanochains, nanofibers, nanotubes, nanorings, nanocoils, and quasi-one-dimensional (1D) van der Waals materials. Accordingly, the fabricated routes, shielding performances, and EM waves attenuation mechanism of the 1D metallic, magnetic, and dielectric nanofiller-based composites are summarized. It is found that the dominant shielding mechanism of most of the 1D metal-based EMI composites is reflection loss, while that of 1D magnetic and dielectric nanomaterials-based EMI composites is absorption loss caused by interfacial polarization, natural resonance, eddy current, and multiple scattering. Finally, the challenges and prospects of 1D nanofiller-based composites with a tunable architecture and composition are put forward, aiming to give a guideline for the next generation of high-performance EMI shielding materials. [ABSTRACT FROM AUTHOR]

Integration of nanolayered metal chalcogenides with wide-bandgap semiconductors forming pn heterojunction leads to the way of high-performance photodetection. This work demonstrates the fabrication of a few nanometer thick Molybdenum diselenide (MoSe2)/Mg-doped Gallium Nitride (p-GaN) heterostructure for light detection purposes. The device exhibits low noise broadband spectral response from ultraviolet to near-infrared range (300â€"950 nm). The band-alignment and the charge transfer at the MoSe2/p-GaN interface promote self-powered photodetection with high photocurrent to dark current ratio of 2000 and 1000 at 365 nm and 640 nm, respectively. A high responsivity of 130 A Wâˆ'1, detectivity of 4.8 × 1010 Jones, and low noise equivalent power of 18 fW/Hz1/2 at 365 nm is achieved at an applied bias of 1 V. Moreover, the transient measurements reveal a fast rise/fall time of 407/710 ÎĽ sec for the fabricated device. These outcomes exemplify the viability of MoSe2/p-GaN heterostructure for high-speed and low-noise broadband photodetector applications. [ABSTRACT FROM AUTHOR]

We introduce in the many-body GW scheme the modulation of the screened Coulomb interaction W arising from the macroscopic dielectric response in the infrared. We derive expressions for the polaron binding energies, the renormalization of the effective masses and for the electron and hole relaxation times. Electron and hole mobilities are then obtained from the incorporation of appropriate scattering rules. Zinc-blende GaN and orthorhombic MAPbI3 are used as test beds finding fair agreement with results from rigorous electron-phonon coupling approaches. Although limited to polar phonons, our method has a negligible computational cost. [ABSTRACT FROM AUTHOR]

Electron spin qubits are a promising platform for quantum computation. Environmental noise impedes coherent operations by limiting the qubit relaxation (T1) and dephasing (Tϕ) times. There are multiple sources of such noise, which makes it important to devise experimental techniques that can detect the spatial locations of these sources and determine the type of source. In this paper, we propose that anisotropy in T1 and Tϕ with respect to the direction of the applied magnetic field can reveal much about these aspects of the noise. We investigate the anisotropy patterns of charge noise, evanescent-wave Johnson noise, and hyperfine noise in hypothetical devices. It is necessary to have a rather well-characterized sample to get the maximum benefit from this technique. The general anisotropy patterns are elucidated. We calculate the expected anisotropy for a particular model of a Si/SiGe quantum dot device. [ABSTRACT FROM AUTHOR]

The effect of annealing on the parameters of 4H-SiC Schottky diodes irradiated with electrons at a high temperature is studied for the first time. The electron energy is 0.9 MeV, irradiation is carried out at temperatures of 23, 300, and 500°C with fluences Φ in the 1 × 1016–1.3 × 1017 cm–2 range. The results of annealing samples irradiated at high temperatures differ qualitatively from the results of annealing samples irradiated with the same fluence at room temperature. The results indicate that, under high-temperature ("hot") irradiation, the spectrum of radiation-induced defects introduced in SiC differs significantly from the spectrum of defects introduced at room temperature. The effect of reverse annealing, when the resistance of the base of the diode does not fall but increases as a result of annealing, was discovered for large values of Φ at irradiation temperatures of 300 and 500°C. [ABSTRACT FROM AUTHOR]

Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of Ill-nitrides requires reliable methods for strain investigation. In this work, we reveal, that the linear model based on the experimental data limited to within a small range of biaxial strains (< 0.2%), which is widely used for the non-destructive Raman study of strain with nanometer-scale spatial resolution is not valid for the binary wurtzite-structure group-III nitrides GaN and AlN. Importantly, we found that the discrepancy between the experimental values of strain and those calculated via Raman spectroscopy increases as the strain in both GaN and AlN increases. Herein, a new model has been developed to describe the strain-induced Raman frequency shift in GaN and AlN for a wide range of biaxial strains (up to 2.5%). Finally, we proposed a new approach to correlate the Raman frequency shift and strain, which is based on the lattice coherency in the epitaxial layers of superlattice structures and can be used for a wide range of materials. [ABSTRACT FROM AUTHOR]

Nonlinear oscillations in micro- and nanoelectromechanical systems have emerged as an exciting research area in recent years due to their promise in realizing low-power, scalable, and reconfigurable mechanical memory and logic devices. Here, we report ultralow-power mechanical memory operations utilizing the nonlinear oscillation regime of GaN microcantilevers with embedded piezotransistive AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers. Switching between the high and low oscillatory states of the nonlinear oscillation regime was demonstrated using a novel phase-controlled opto-mechanical excitation setup, utilizing a piezo actuator and a pulsed laser as the primary and secondary excitation sources, respectively. Laser-based photoacoustic excitation was amplified through plasmonic absorption in Au nanoparticles deposited on a transistor. Thus, the minimum switching energy required for reliable memory operations was reduced to less than a picojoule (pJ), which translates to one of the lowest ever reported, when normalized for mass. [ABSTRACT FROM AUTHOR]

In this paper, a junction-less charge plasma (CP) double-drift region (DDR) impact avalanche transit time (IMPATT) diode structure has been proposed for realizing a high-power and efficient terahertz (THz) source. A comprehensive two-dimensional (2-D) self-consistent quantum drift-diffusion (SCQDD) model has been developed by the author to study the static and THz performance of 4H-SiC based CP-DDR source designed to operate at 1.0 THz. Comparative studies on the DC and THz performance of the proposed device and conventionally doped vertical DDR IMPATT device reveal that the proposed CP-DDR can be the potential alternative of the conventional DDRs (C-DDRs), especially at the THz regime. The proposed THz CP-DDR source can be exclusively preferable over its conventional counterparts due to its easier and less complicated fabrication steps as well as equivalent performance capability with respect to the THz C-DDR sources. [ABSTRACT FROM AUTHOR]

Defects can significantly modify the electro-optical characteristics of InGaN light-emitting diodes (LEDs); however, modeling the impact of defects on the electrical characteristics of LEDs is not straightforward. In this paper, we present an extensive investigation and modeling of the impact of defects on the electrical characteristics of InGaN-based LEDs, as a function of the thickness of the quantum well (QW). First, we demonstrate that the density of defects in the active region of III-N LEDs scales with increasing thickness of the InGaN QW. Since device layers with high indium content tend to incorporate more defects, we ascribed this experimental evidence to the increased volume of defects-rich InGaN associated to thicker InGaN layers. Second, we demonstrate that the current–voltage characteristics of the devices are significantly influenced by the presence of defects, especially in the sub turn-on region. Specifically, we show that the electrical characteristics can be effectively modeled in a wide current range (from pA to mA), by considering the existence of trap-assisted tunneling processes. A good correspondence is obtained between the experimental and simulated electrical characteristics (I–V), by using—in the simulation—the actual defect concentrations/activation energies extracted from steady-state photocapacitance, instead of generic fitting parameters. [ABSTRACT FROM AUTHOR]

This work presents an useful tool for constructing the solution of steady-state heat transfer problems, with temperature-dependent thermal conductivity, by means of the solution of Poisson equations. Specifically, it will be presented a procedure for constructing the solution of a nonlinear second-order partial differential equation, subjected to Robin boundary conditions, by means of a sequence whose elements are obtained from the solution of very simple linear partial differential equations, also subjected to Robin boundary conditions. In addition, an a priori upper bound estimate for the solution is presented too. Some examples, involving temperature-dependent thermal conductivity, are presented, illustrating the use of numerical approximations. [ABSTRACT FROM AUTHOR]

Achieving high interface thermal conductance is one of the biggest challenges in the nanoscale heat transport of GaN-based devices such as light emitting diodes (LEDs), and high electron mobility transistors (HEMTs). In this work, we experimentally measured thermal boundary conductance (TBC) at interfaces between GaN and the substrates with AuSn alloy as a commonly-used adhesive layer by time-domain thermoreflectance (TDTR). We find that the TBCs of GaN/Ti/AuSn/Ti/Si, GaN/Ti/AuSn/Ti/SiC, and GaN/Ti/AuSn/Ti/diamond, are 16.5, 14.8, and 13.2 MW·m−2·K−1 at room temperature, respectively. Our measured results show that the TBC of GaN/Ti/AuSn/Ti/SiC interface is inferior to the TBC of pristine GaN/SiC interface, due to the large mismatch of phonon modes between AuSn/Ti and substrates, shown as the difference of Debye temperature of two materials. Overall, we measured the TBC at interface between GaN and thermal conductive substrates, and provided a guideline for designing the interface between GaN and substrate at HEMT from a thermal management point of view. [ABSTRACT FROM AUTHOR]

In this work, Al0.83In0.17N/GaN/Al0.18Ga0.82N/GaN epitaxial layers used for the fabrication of double-channel metal–oxide–semiconductor high-electron mobility transistors (MOSHEMTs) were grown on silicon substrates using a metalorganic chemical vapor deposition system (MOCVD). A sheet electron density of 1.11 × 1013 cm−2 and an electron mobility of 1770 cm2/V-s were obtained. Using a vapor cooling condensation system to deposit high insulating 30-nm-thick Ga2O3 film as a gate oxide layer, double-hump transconductance behaviors with associated double-hump maximum extrinsic transconductances (gmmax) of 89.8 and 100.1 mS/mm were obtained in the double-channel planar MOSHEMTs. However, the double-channel devices with multiple-mesa-fin-channel array with a gmmax of 148.9 mS/mm exhibited single-hump transconductance behaviors owing to the better gate control capability. Moreover, the extrinsic unit gain cutoff frequency and maximum oscillation frequency of the devices with planar channel and multiple-mesa-fin-channel array were 5.7 GHz and 10.5 GHz, and 6.5 GHz and 12.6 GHz, respectively. Hooge's coefficients of 7.50 × 10−5 and 6.25 × 10−6 were obtained for the devices with planar channel and multiple-mesa-fin-channel array operating at a frequency of 10 Hz, drain–source voltage of 1 V, and gate–source voltage of 5 V, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials may play an important role in future photodetectors due to their natural atom-thin body thickness, unique quantum confinement, and excellent electronic and photoelectric properties. Semimetallic graphene, semiconductor black phosphorus, and transition metal dichalcogenides possess flexible and adjustable bandgaps, which correspond to a wide interaction spectrum ranging from ultraviolet to terahertz. Nevertheless, their absorbance is relatively low, and it is difficult for a single material to cover a wide spectrum. Therefore, the combination of phototransistors based on 2D hybrid structures with other material platforms, such as quantum dots, organic materials, or plasma nanostructures, exhibit ultra-sensitive and broadband optical detection capabilities that cannot be ascribed to the individual constituents of the assembly. This article provides a comprehensive and systematic review of the recent research progress of 2D material photodetectors. First, the fundamental detection mechanism and key metrics of the 2D material photodetectors are introduced. Then, the latest developments in 2D material photodetectors are reviewed based on the strategies of photocurrent enhancement. Finally, a design and implementation principle for high-performance 2D material photodetectors is provided, together with the current challenges and future outlooks. [ABSTRACT FROM AUTHOR]

Engineering materials to include nanoscale porosity or other nanoscale structures has become a well-established strategy for enhancing the thermoelectric performance of dielectrics. However, the approach is only considered beneficial for materials where the intrinsic phonon mean-free path is much longer than that of the charge carriers. As such, the approach would not be expected to provide significant performance gains in polycrystalline semiconducting alloys, such as SixGe1-x, where mass disorder and grains provide strong phonon scattering. In this manuscript, we demonstrate that the addition of nanoscale porosity to even ultrafine-grained Si 0.8 Ge 0.2 may be worthwhile. The semiclassical Boltzmann transport equation was used to model electrical and phonon transport in polycrystalline Si 0.8 Ge 0.2 containing prismatic pores perpendicular to the transport current. The models are free of tuning parameters and were validated against experimental data. The models reveal that a combination of pores and grain boundaries suppresses phonon conductivity to a magnitude comparable with the electronic thermal conductivity. In this regime, ZT can be further enhanced by reducing carrier concentration to the electrical and electronic thermal conductivity and simultaneously increasing thermopower. Although increases in ZT are modest, the optimal carrier concentration is significantly lowered, meaning semiconductors need not be so strongly supersaturated with dopants. [ABSTRACT FROM AUTHOR]