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  • JOURNAL OF APPLIED PHYSICS
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2013 2016

The optical properties of bulk InAs[subscript 0.936]Bi[subscript 0.064] grown by molecular beam epitaxy on a (100)-oriented GaSb substrate are measured using spectroscopic ellipsometry. The index of refraction and absorption coefficient are measured over photon energies ranging from 44 meV to 4.4 eV and are used to identify the room temperature bandgap energy of bulk InAs[subscript 0.936]Bi[subscript 0.064] as 60.6 meV. The bandgap of InAsBi is expressed as a function of Bi mole fraction using the band anticrossing model and a characteristic coupling strength of 1.529 eV between the Bi impurity state and the InAs valence band. These results are programmed ...

Contributors
Webster, Preston, Shalindar Christaj, Arvind Joshua Jaydev, Riordan, Nathaniel, et al.
Created Date
2016-06-08

Recently, near-field thermal radiation has attracted much attention in several fields since it can exceed the Planck blackbody limit through the coupling of evanescent waves. In this work, near-field radiative heat transfer between two semi-infinite dual uniaxial electromagnetic metamaterials with two different material property sets is theoretically analyzed. The near-field radiative heat transfer is calculated using fluctuational electrodynamics incorporated with anisotropic wave optics. The underlying mechanisms, namely, magnetic hyperbolic mode, magnetic surface polariton, electrical hyperbolic mode, and electrical surface polariton, between two homogeneous dual uniaxial electromagnetic metamaterials are investigated by examining the transmission coefficient and the spectral heat flux. The ...

Contributors
Chang, Jui-Yung, Basu, Soumyadipta, Yang, Yue, et al.
Created Date
2016-06-07

We report on a new numerical approach for multi-band drift within the context of full band Monte Carlo (FBMC) simulation and apply this to Si and InAs nanowires. The approach is based on the solution of the Krieger and Iafrate (KI) equations [J. B. Krieger and G. J. Iafrate, Phys. Rev. B 33, 5494 (1986)], which gives the probability of carriers undergoing interband transitions subject to an applied electric field. The KI equations are based on the solution of the time-dependent Schrödinger equation, and previous solutions of these equations have used Runge-Kutta (RK) methods to numerically solve the KI equations. ...

Contributors
Hathwar, Raghuraj, Saraniti, Marco, Goodnick, Stephen, et al.
Created Date
2016-07-29

The properties of InAs quantum dots (QDs) have been studied for application in intermediate band solar cells. It is found that suppression of plastic relaxation in the QDs has a significant effect on the optoelectronic properties. Partial capping plus annealing is shown to be effective in controlling the height of the QDs and in suppressing plastic relaxation. A force balancing model is used to explain the relationship between plastic relaxation and QD height. A strong luminescence has been observed from strained QDs, indicating the presence of localized states in the desired energy range. No luminescence has been observed from plastically ...

Contributors
Xie, Hongen, Prioli Menezes, Rodrigo, Fischer, Alec M., et al.
Created Date
2016-07-15

Modulated reflectance (contactless electroreflectance (CER), photoreflectance (PR), and piezoreflectance (PzR)) has been applied to study direct optical transitions in bulk MoS[subscript 2], MoSe[subscript 2], WS[subscript 2], and WSe[subscript 2]. In order to interpret optical transitions observed in CER, PR, and PzR spectra, the electronic band structure for the four crystals has been calculated from the first principles within the density functional theory for various points of Brillouin zone including K and H points. It is clearly shown that the electronic band structure at H point of Brillouin zone is very symmetric and similar to the electronic band structure at K ...

Contributors
Kopaczek, J., Polak, M. P., Scharoch, P., et al.
Created Date
2016-06-21

Chemical vapor deposition methods were developed, using stoichiometric reactions of specialty Ge[subscript 3]H[subscript 8] and SnD[subscript 4] hydrides, to fabricate Ge[subscript 1-y]Sn[subscript y] photodiodes with very high Sn concentrations in the 12%–16% range. A unique aspect of this approach is the compatible reactivity of the compounds at ultra-low temperatures, allowing efficient control and systematic tuning of the alloy composition beyond the direct gap threshold. This crucial property allows the formation of thick supersaturated layers with device-quality material properties. Diodes with composition up to 14% Sn were initially produced on Ge-buffered Si(100) featuring previously optimized n-Ge/i-Ge[subscript 1-y]Sn[subscript y]/p-Ge[subscript 1-z]Sn[subscript z] type ...

Contributors
Senaratne, Charutha Lasitha, Wallace, Patrick, Gallagher, John, et al.
Created Date
2016-07-13

The optical properties of intersubband transition in a semipolar AlGaN/GaN single quantum well (SQW) are theoretically studied, and the results are compared with polar c-plane and nonpolar m-plane structures. The intersubband transition frequency, dipole matrix elements, and absorption spectra are calculated for SQW on different semipolar planes. It is found that SQW on a certain group of semipolar planes (55° < θ < 90° tilted from c-plane) exhibits low transition frequency and long wavelength response with high absorption quantum efficiency, which is attributed to the weak polarization-related effects. Furthermore, these semipolar SQWs show tunable transition frequency and absorption wavelength with ...

Contributors
Fu, Houqiang, Lu, Zhijian, Huang, Xuangqi, et al.
Created Date
2016-05-05

InGaN semiconductors are promising candidates for high-efficiency next-generation thin film solar cells. In this work, we study the photovoltaic performance of single-junction and two-junction InGaN solar cells using a semi-analytical model. We analyze the major loss mechanisms in InGaN solar cell including transmission loss, thermalization loss, spatial relaxation loss, and recombination loss. We find that transmission loss plays a major role for InGaN solar cells due to the large bandgaps of III-nitride materials. Among the recombination losses, Shockley-Read-Hall recombination loss is the dominant process. Compared to other III-V photovoltaic materials, we discovered that the emittance of InGaN solar cells is ...

Contributors
Huang, Xuangqi, Fu, Houqiang, Chen, Hong, et al.
Created Date
2016-06-01

In this paper, we report on the highly conductive layer formed at the crystalline γ-alumina/SrTiO[subscript 3] interface, which is attributed to oxygen vacancies. We describe the structure of thin γ-alumina layers deposited by molecular beam epitaxy on SrTiO3 (001) at growth temperatures in the range of 400–800 °C, as determined by reflection-high-energy electron diffraction, x-ray diffraction, and high-resolution electron microscopy. In situ x-ray photoelectron spectroscopy was used to confirm the presence of the oxygen-deficient layer. Electrical characterization indicates sheet carrier densities of ∼1013 cm−2 at room temperature for the sample deposited at 700 °C, with a maximum electron Hall mobility ...

Contributors
Kormondy, Kristy J., Posadas, Agham B., Ngo, Thong Q., et al.
Created Date
2015-03-07

The current work explores the crystalline perovskite oxide, strontium hafnate, as a potential high-k gate dielectric for Ge-based transistors. SrHfO3 (SHO) is grown directly on Ge by atomic layer deposition and becomes crystalline with epitaxial registry after post-deposition vacuum annealing at ∼700 °C for 5 min. The 2 × 1 reconstructed, clean Ge (001) surface is a necessary template to achieve crystalline films upon annealing. The SHO films exhibit excellent crystallinity, as shown by x-ray diffraction and transmission electron microscopy. The SHO films have favorable electronic properties for consideration as a high-k gate dielectric on Ge, with satisfactory band offsets ...

Contributors
McDaniel, Martin D., Hu, Chengqing, Lu, Sirong, et al.
Created Date
2015-02-07