Cross-plane Seebeck coefficient of ErAs : InGaAs/InGaAlAs superlattices

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

Demonstration of electron filtering to increase the Seebeck coefficient in In0.53Ga0.47As/In0.53Ga0.28Al0.19As superlattices

In this paper, we explore electron filtering as a technique to increase the Seebeck coefficient and the thermoelectric power factor of heterostructured materials over that of the bulk. We present a theoretical model in which the Seebeck coefficient and the power factor can be increased in an In0.53Ga0.47As-based composite material. Experimental measurements of the cross-plane Seebeck coefficient are presented and confirm the importance of the electron filtering technique to decouple the electrical conductivity and Seebeck coefficient to increase the thermoelectric power factor

Experimental and modelling study of InGaBiAs/InP alloys with up to 5.8% Bi, and with Delta(so) > E-g

Temperature dependent photo-modulated reflectance is used to measure the band gap Eg and spin–orbit splitting energy Δso in dilute-Bi In0.53Ga0.47As1-xBix/InP for 1.2% ≤ x ≤ 5.8%. At room temperature, Eg decreases with increasing Bi from 0.65 to 0.47 eV (∼2.6 μm), while Δso increases from 0.42 to 0.62 eV, leading to a crossover between Eg and Δso around 3.8% Bi. The 5.8% Bi sample is the first example of this alloy where Δso > Eg has been confirmed at all temperatures. The condition Δso > Eg is important for suppressing hot-hole-producing non-radiative Auger recombination and inter-valence band absorption losses and so holds promise for the development of mid-infra-red devices based on this material system. The measured variations of Eg and Δso as a function of Bi content at 300 K are compared to those calculated using a 12-band k.p Hamiltonian which includes valence band anti-crossing effects. The Eg results as a function of temperature are fitted with the Bose–Einstein model. We also look for evidence to support the prediction that Eg in dilute bismides may show a reduced temperature sensitivity, but find no clear indication of that

Temperature and Bi-concentration dependence of the bandgap and spin-orbit splitting in InGaBiAs/InP semiconductors for mid-infrared applications

Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ > E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ (x, T) in InGa BiAs/InP samples for 0 x 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence of a decreased dE/dT (≈0.34 ± 0.06 meV/K in all samples) we find Δ > E for x > 3.3-4.3. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 American Institute of Physics

STRUCTURAL HIERARCHY OF BORON NITRIDE AND ITS CONNECTION WITH PROPERTIES

The methods for preparation of the electron microscopy objects by an ion etching method has been developed. The results of the structural investigations have been generalized as a universal model of the structural hierarchy for the pyrolytic boron nitride; by means of this model the conduction of the basic structural elements has been evaluated and its anisotropy has been determined. The thermic stability area and critical dimensions of the double formations with symmetry of the fifth order shape have been determined. The crystal-geometric diagram has been drawn up, and the mechanism of its formation has been proposed. The high radiation stability of the materials structure has been specifiedAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

InGaBiAs/InP semiconductors for mid-infrared applications: Dependence of bandgap and spin-orbit splitting on temperature and bismuth content

Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ>E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ(x, T) in InGa BiAs/InP samples for 0≤x≤0.032 by optical spectroscopy. While we find no clear evidence of a decreased dE /dT (≈0.33±0.07meV/K in all samples) we find Δ>E for x>3.3-4.3%. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 IEEE