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In this work, we demonstrate atomic-layer-deposited (ALD) single-channel indium oxide (In2O3) gate-all-around (GAA) nanoribbon field-effect transistors (FETs) in a back-end-of-line (BEOL) compatible process. A maximum on-state current (ION) of 19.3 mA/ $\mu \text{m}$ (near 20 mA/ $\mu \text{m}$) and an on/off ratio of 106 are achieved in an In2O3 GAA nanoribbon FET with a channel thickness (TIO) of 3.1 nm, channel length (Lch) of 40 nm, channel width (Wch) of 30 nm and dielectric HfO2 of 5 nm. Short-pulse measurements are applied to mitigate the self-heating effect induced by the ultra-high drain current flowing in the ultra-thin channel layer. The record high drain current obtained from an In2O3 FET is about one order of magnitude higher than any conventional single-channel semiconductor FETs. This extraordinary drain current and its related on-state performance demonstrate that ALD In2O3 is a promising oxide semiconductor channel with great opportunities in BEOL compatible monolithic 3D integration. [ABSTRACT FROM AUTHOR]

The electrostatic properties of nanowire field effect transistors with triangular cross sections were investigated. The Poisson equation was solved for these structures; furthermore, two properties of the nanowire field effect transistors, the gate capacitance and current versus gate voltage, were calculated. The simulation results yielded the type, mobility, and concentration of the carriers, as well as the Ohmic contact resistance of the wire transistor. We examined how wire capacitance depends on various parameters: wire diameter, gate oxide thickness, charge density, and shape. It is shown that the capacitance of a triangular nanowire is less than that of a cylindrical nanowire of the same size, which could be significant in structures with thin gate oxides. The simulation results were compared with the previously reported experimental data on GaN nanowires. [ABSTRACT FROM AUTHOR]

A detailed theory of nonisothermal electron transport perpendicular to multilayer superlattice structures is presented. The current–voltage (I–V) characteristics and the cooling power density are calculated using Fermi–Dirac statistics, density-of-states for a finite quantum well and the quantum mechanical reflection coefficient. The resulting equations are valid in a wide range of temperatures and electric fields. It is shown that conservation of lateral momentum plays an important role in the device characteristics. If the lateral momentum of the hot electrons is conserved in the thermionic emission process, only carriers with sufficiently large kinetic energy perpendicular to the barrier can pass over it and cool the emitter junction. However, if there is no conservation of lateral momentum, the number of electrons participating in a thermionic emission will increase. This has a significant effect on the I–V measurements as well as the cooling characteristics. Theoretical calculations are compared with the experimental dark current characteristics of quantum well infrared photodetectors and good agreement over a wide temperature range for a variety of superlattice structures is obtained. In contrast with earlier studies, it is shown that lateral momentum is conserved for the case of electron transport in planar semiconductor barriers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A device fabrication and measurement method utilizing a SiO2–SiO2 covalent bonding technique is presented for high-temperature thermoelectric characterization of thin-film III–V semiconductor materials that suffer from the side-effect of substrate conduction at high temperatures. The proposed method includes complete substrate removal, high-temperature surface passivation, and metallization with a Ti-W-N diffusion barrier. A thermoelectric material, thin-film ErAs:InGaAlAs metal/semiconductor nanocomposite grown on a lattice-matched InP substrate by molecular beam epitaxy, was transferred onto a sapphire substrate using the oxide bonding technique at 300°C, and its original InP substrate, which is conductive at high temperatures, was removed. Electrical conductivities and Seebeck coefficients were measured from room temperature to 840 K for this material on both the InP and sapphire substrates, and the measurement results clearly show that the InP substrate effect was eliminated for the sample on the sapphire substrate. A strain experiment has been conducted to investigate the effect of strain on electrical conductivity. [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) electrothermal model was developed to study the InP-based thin-film In0.53 Ga0.47 As/In0.52 Al0.48 As superlattice (SL) microre- frigerators for various device sizes, ranging from 40 × 40 to 120 × 120 μm². We discussed both the maximum cooling and cooling power densities (CPDs) for experimental devices, analyzed their nonidealities, and proposed an optimized structure. The simulation results demonstrated that the experimental devices with an optimized structure can achieve a maximum cooling of 3 ° C, or equivalently, a CPD over 300 W/cm². Furthermore, we found it was possible to achieve a maximum cooling of over 10 °C; equivalently, a CPD over 900 W/cm², when the figure of merit (ZT) of InGaAs/InAlAs SL was enhanced five times with nonconserved lateral momentum structures. Besides monolithic growth, we also proposed a fusion bonding scheme to simply bond the microrefrigerator chip on the back of the hot spots, defined as two-chip integration model in this paper. The cooling effect of this model was analyzed using ANSYS simulations. [ABSTRACT FROM AUTHOR]

We investigate thermal effects in widely tunable laser transmitters based on an integrated single chip design. The chip contains a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption modulator (EAM). The thermal impedance of the ridge structure is evaluated through simulation and experiment, and thermal crosstalk between sections is examined. Heating of the mirrors by neighboring sections is found to result in unintentional offsets in wavelength tuning. Thermal effects in the EAM are examined in depth. A positive feedback mechanism causes local temperature rise at the modulator input, with the potential to trigger catastrophic thermal runaway. A self-consistent finite-element model is developed to simulate the EAM temperature profile and device performance. This model is used to optimize the device, resulting in integrated EAMs that achieve a dissipated power limit in excess of 300 mW. [ABSTRACT FROM AUTHOR]

The hydrodynamic model of electron transport in semiconductors is analyzed and, in analogy with vortices in fluid mechanics, the curl of electron velocity is defined as electron vorticity, and the transport equation for the electron vorticity is derived. Aside from the classical hydrodynamic sources of vorticity, collision terms in the continuity and momentum equations are identified as sources and sinks of electron vorticity. Similar to three-dimensional fluid flows there is a vortex stretching term in the vorticity equation. This term could be responsible for the possible cascade of electron kinetic energy to small scales and formation of chaotic turbulent electron transport regimes. A scale analysis of the electron vorticity equation is performed and the relative order of magnitude of each sources of vorticity is found. This analysis and the calculation of electron mean-free-path due to electron–electron and electron–phonon scatterings characterize a transport regime with significant electron vorticity effects. Furthermore, conditions for observation of electron vortices in semiconductor devices are predicted. [ABSTRACT FROM AUTHOR]

Modern, high-density integrated circuits (IC) typically use a flip chip bonding technique to increase performance on a greater number of interconnects. In doing so, the active devices of the IC are hidden under the exposed substrate, which precludes the use of typical surface thermal characterization techniques. A near infrared thermoreflectance method is described such that the temperature of active semiconductor devices can be measured through the substrate. Experimental results were obtained through a 200μm thick silicon substrate. Temperature resolution of 0.1K and spatial resolution of 5μm has been achieved. The Fabry–Perot effect, due to multiple reflections between the device and the back of the substrate, has been experimentally and theoretically analyzed. Techniques to enhance the spatial resolution will be discussed. [Copyright &y& Elsevier]

We show theoretically that the thermoelectric power factor can be enhanced in degenerate semiconductors when embedded nanoparticles donate carriers to the matrix and replace conventional impurity dopants as scattering centers. Nanoparticle scattering rates calculated by the partial wave method indicate a mobility enhancement over materials with equivalent doping by isolated ionized impurities while the Seebeck coefficient remains nearly intact. We find that the thermoelectric power factor of In0.53Ga0.47As from 300 K to 800 K is enhanced by 15% - 30% by nanoparticles 3-4 nm in diameter. [ABSTRACT FROM AUTHOR]

We utilize the transient Harman technique to measure the thermoelectric figure of merit of thin films. A device structure is designed and fabricated to extract the thermoelectric properties of 20 μm thick film composed of InGaAlAs semiconductor with embedded ErAs nanoparticles. High-speed voltage measurements with 63 dB of dynamic range and 200 ns resolution are achieved. Surface temperature measurements of the devices are used to extract the cross-plane Seebeck coefficient and thermal conductivity of the thermoelectric material. Self-consistent finite-element simulations of the three-dimensional temperature distributions in the active devices are in close agreement with the experimental thermal maps. [ABSTRACT FROM AUTHOR]

Nonlinear Peltier coefficient of a doped InGaAs semiconductor is calculated numerically using the Monte Carlo technique. The Peltier coefficient is also obtained analytically for single parabolic band semiconductors assuming a shifted Fermi-Dirac electronic distribution under an applied bias. Analytical results are in agreement with numerical simulations. Key material parameters affecting the nonlinear behavior are doping concentration, effective mass, and electron-phonon coupling. Current density thresholds at which nonlinear behavior is observable are extracted from numerical data. It is shown that the nonlinear Peltier effect can be used to enhance cooling of thin film microrefrigerator devices especially at low temperatures. [ABSTRACT FROM AUTHOR]

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

A tall barrier superlattice structure based on mercury cadmium telluride material system is proposed that can achieve a large effective thermoelectric figure of merit (ZTmax∼3) at cryogenic temperatures. Calculations based on the Boltzmann transport equation taking into account the quantum mechanical electron transmission show that the Seebeck coefficient can be increased significantly at low temperatures with the use of nonplanar barriers as the thermal spreading of the electron density is tightened around the Fermi level. This provides a better asymmetric differential conductivity around the Fermi level close to the top of the barrier. Consequently, a high thermoelectric power factor is produced resulting in a large ZT. [ABSTRACT FROM AUTHOR]

We report a wafer scale approach for the fabrication of thin-film power generators composed of arrays of 400 p and n type ErAs:InGaAs/InGaAlAs superlattice thermoelectric elements. The elements incorporate ErAs metallic nanoparticles into the semiconductor superlattice structure to provide charge carriers and create scattering centers for phonons. p- and n-type ErAs:InGaAs/InGaAlAs superlattices with a total thickness of 5 μm were grown on InP substrate using molecular beam epitaxy. The cross-plane Seebeck coefficients and cross-plane thermal conductivity of the superlattice were measured using test pattern devices and the 3ω method, respectively. Four hundred element power generators were fabricated from these 5 μm thick, 200 μm×200 μm in area superlattice elements. The output power was over 0.7 mW for an external resistor of 100 Ω with a 30 K temperature difference drop across the generator. We discuss the limitations to the generator performance and provide suggestions for improvements. [ABSTRACT FROM AUTHOR]

A three-dimensional electrothermal model has been developed to investigate the spatial resolution of the scanning thermoelectric microscopy (SThEM). We found that if the electrical resistivity of the sample changes abruptly, the SThEM will measure a voltage close to the local thermoelectric voltage where electrical resistivity is relatively low, rather than a simple weighted average of the thermoelectric voltage distribution based on the temperature profile. This is due to the presence of internal currents in the sample. The spatial resolution of the Seebeck profiling is limited by the finite value of the phonon mean free path of the sample and the tip size of the microscopy. With a tip size around 1 nm, the scanning thermoelectric microscopy can achieve a spatial resolution of the physical limit defined by the statistical nature of the charge carrier and phonon behavior in a very small region. [ABSTRACT FROM AUTHOR]

In this article, we show how relativistic α-stable processes can be used to explain quasiballistic heat conduction in semiconductors. This is a method that can fit experimental results of ultrafast laser heating in alloys. It also provides a connection to a rich literature on the Feynman-Kac formalism and random processes that transition from a stable Lévy process on short time and length scales to the Brownian motion at larger scales. This transition was captured by a heuristic truncated Lévy distribution in earlier papers. The rigorous Feynman-Kac approach is used to derive sharp bounds for the transition kernel. Future directions are briefly discussed. [ABSTRACT FROM AUTHOR]

The article focuses on electronic device failure analysis and semiconductor device application. It highlights a noninvasive thermal imaging approach based on the thermoreflectance principle which can meet the spatial resolution requirements for advanced devices as well as provides temporal resolution in the nanosecond range for analyzing time dependent thermal scenarios.

Materials with embedded nanoparticlesare of considerable interest for thermoelectric applications. Here,we experimentally characterize the effect of nanoparticles on therecently discovered Lévy phonon transport in semiconductoralloys. The fractal space dimension α ≈ 1.55 of quasiballistic(superdiffusive) heat conduction in (ErAs)x:InGaAlAs is virtually independent of the Er content 0.001 < x< 0.1 but instead controlled by alloy scattering ofthe host matrix. The increased nanoparticle concentration does reducethe diffusive recovery length by an order of magnitude. The bulk conductivitydrops by 3-fold, in close agreement with a Callaway model. Our resultsmay provide helpful hints toward engineering superdiffusive heattransport similar to what has been achieved with light in Lévyglasses. [ABSTRACT FROM AUTHOR]

Thermal interface (Kapitza) resistance expresses how hard it is for heat to flow across material junctions inside multilayer structures. This quantity plays a crucial role in the thermal performance of nanoscale devices but is still poorly understood. Here we show that conventional Fourier-based metrology overestimates metal/semiconductor resistances by up to threefold due to misinterpretation of ballistic heat flow modes. We achieve improved identification and a different physical insight with a truncated Lévy formalism. This approach properly distinguishes interfacial dynamics from nearby quasiballistic heat flow suppression in the semiconductor. Unlike conventionally extracted values, interface resistances obtained with our new approach are independent of laser modulation frequency, as physically appropriate, and much more closely approach theoretical predictions. [ABSTRACT FROM AUTHOR]

We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices. [ABSTRACT FROM AUTHOR]