PRB: Semiconductors I: bulk

Measurements of the Einstein relation in doped and undoped molecular thin films

2008-05-02T00:00:00-04:00

Author(s): O. Tal, I. Epstein, O. Snir, Y. Roichman, Y. Ganot, C. K. Chan, A. Kahn, N. Tessler, and Y. Rosenwaks
We present the Kelvin probe force microscopy measurements of the Einstein relation, i.e., the relation between the diffusion coefficient of charge carriers and their mobility, in undoped and doped disordered organic thin films. The theoretical prediction of a large deviation of the Einstein relation...

[Phys. Rev. B 77, 201201] Published Fri May 02, 2008

Polarization-resolved phonon-assisted optical transitions of bound excitons in wurtzite GaN

2008-05-02T00:00:00-04:00

Author(s): A. A. Toropov, Yu. E. Kitaev, T. V. Shubina, P. P. Paskov, J. P. Bergman, B. Monemar, and A. Usui
The selection rules of phonon-assisted optical transitions of bound excitons in bulk wurtzite GaN are studied both experimentally and theoretically. The linearly polarized photoluminescence is detected within the phonon replicas of the lines of impurity bound excitons in the geometry, when the light...
[Phys. Rev. B 77, 195201] Published Fri May 02, 2008

Thermodynamic states and phase diagrams for bulk-incoherent, bulk-coherent, and epitaxially-coherent semiconductor alloys: Application to cubic (Ga,In)N

Jefferson Z. Liu and Alex Zunger — 2008-05-01T00:00:00-04:00

Author(s): Jefferson Z. Liu and Alex Zunger
The morphology and microstructure of A_{1−x} B_{x} C semiconductor alloys depend on the type of thermodynamic states established during growth. We distinguish three main cases: (i) bulk-incoherent structures occur when the alloy grows without being coherent with an underlying substrate and when ea...
[Phys. Rev. B 77, 205201] Published Thu May 01, 2008

Mean-field model for electron-glass dynamics

Ariel Amir, Yuval Oreg, and Yoseph Imry — 2008-04-30T00:00:00-04:00

Author(s): Ariel Amir, Yuval Oreg, and Yoseph Imry
We study a microscopic mean-field model for the dynamics of the electron glass near a local equilibrium state. Phonon-induced tunneling processes are responsible for generating transitions between localized electronic sites, which eventually lead to the thermalization of the system. We find that the...
[Phys. Rev. B 77, 165207] Published Wed Apr 30, 2008

Optical absorption and electron paramagnetic resonance of the E_{α}^{′} center in amorphous silicon dioxide

G. Buscarino, R. Boscaino, S. Agnello, and F. M. Gelardi — 2008-04-28T00:00:00-04:00

Author(s): G. Buscarino, R. Boscaino, S. Agnello, and F. M. Gelardi
We report a combined study by optical absorption (OA) and electron paramagnetic resonance (EPR) spectroscopy on the E_{α}^{′} point defect in amorphous silicon dioxide (a-SiO_{2} ) . This defect has been studied in β -ray irradiated and thermally treated oxygen-deficient a-SiO_{2} materials. Our...
[Phys. Rev. B 77, 155214] Published Mon Apr 28, 2008

Role of strain and properties of N clusters at the onset of the alloy limit in GaAs_{1−x} N_{x}

2008-04-28T00:00:00-04:00

Author(s): A. Polimeni, F. Masia, G. Pettinari, R. Trotta, M. Felici, M. Capizzi, A. Lindsay, E. P. O’Reilly, T. Niebling, W. Stolz, and P. J. Klar
In GaAs_{1−x} N_{x} , the band gap energy decreases very rapidly with x and the electron effective mass shows a quite unusual compositional dependence characterized by a sudden doubling for x≅0.1% . In this work, we investigate the origin of this behavior by photoluminescence measurements under ...
[Phys. Rev. B 77, 155213] Published Mon Apr 28, 2008

Intrinsic point defects in aluminum antimonide

Daniel Åberg, Paul Erhart, Andrew J. Williamson, and Vincenzo Lordi — 2008-04-25T00:00:00-04:00

Author(s): Daniel Åberg, Paul Erhart, Andrew J. Williamson, and Vincenzo Lordi
Calculations within density functional theory on the basis of the local density approximation are carried out to study the properties of intrinsic point defects in aluminum antimonide. Special care is taken to address finite-size effects, band gap error, and symmetry reduction in the defect structur...
[Phys. Rev. B 77, 165206] Published Fri Apr 25, 2008

Exciton-spin dephasing and relaxation due to symmetry breaking in two-band bulk semiconductors

M. Gallart, S. Cronenberger, C. Brimont, B. Hönerlage, and P. Gilliot — 2008-04-25T00:00:00-04:00

Author(s): M. Gallart, S. Cronenberger, C. Brimont, B. Hönerlage, and P. Gilliot
The full point group symmetry of a crystal can be broken due to internal or external effective fields. In the study of excitons, such symmetry breaking can lead to a coupling of different exciton states and if a system is prepared in an exciton state with a defined total angular momentum (pseudospin...
[Phys. Rev. B 77, 155212] Published Fri Apr 25, 2008

Electronic surface error in the Si interstitial formation energy

Ann E. Mattsson, Ryan R. Wixom, and Rickard Armiento — 2008-04-25T00:00:00-04:00

Author(s): Ann E. Mattsson, Ryan R. Wixom, and Rickard Armiento
The results for Si interstitial formation energies differ substantially if calculated with quantum Monte Carlo (QMC) or density functional theory (DFT) techniques. In fact, not even DFT results using different exchange-correlation functionals agree well for these energies. We carefully quantify the ...
[Phys. Rev. B 77, 155211] Published Fri Apr 25, 2008

Ultrasonic investigation of ZnSe:V^{2+} and ZnSe:Mn^{2+} : Lattice softening and low-temperature relaxation in crystals with orbitally degenerate states

2008-04-24T00:00:00-04:00

Author(s): V. V. Gudkov, A. T. Lonchakov, V. I. Sokolov, I. V. Zhevstovskikh, and V. T. Surikov
Temperature dependences of elastic moduli and ultrasonic attenuation were investigated in ZnSe:V^{2+} and ZnSe:Mn^{2+} crystals as functions of temperature in the interval of 1.4–100K for frequencies of 52–270MHz . A peak in the attenuation was found in ZnSe:V^{2+} below 4K for fast shear and lo...
[Phys. Rev. B 77, 155210] Published Thu Apr 24, 2008

Copper dihydrogen complex in ZnO

E. V. Lavrov, J. Weber, and F. Börrnert — 2008-04-17T00:00:00-04:00

Author(s): E. V. Lavrov, J. Weber, and F. Börrnert
Local vibrational modes of a copper-dihydrogen complex CuH_{2} in ZnO have been identified by using IR absorption spectroscopy. Two O-H modes at 3347 and 3374 cm^{−1} are observed after Cu in-diffusion at 1200 °C and subsequent hydrogenation at 725 °C in sealed ampoules filled with an H_{2...
[Phys. Rev. B 77, 155209] Published Thu Apr 17, 2008

Resonant Raman-active localized vibrational modes in Al_{y} Ga_{1−y} N_{x} As_{1−x} alloys: Experiment and first-principles calculations

2008-04-16T00:00:00-04:00

Author(s): A. M. Teweldeberhan, G. Stenuit, S. Fahy, E. Gallardo, S. Lazić, J. M. Calleja, J. Miguel-Sánchez, M. Montes, A. Hierro, R. Gargallo-Caballero, A. Guzmán, and E. Muñoz
The localized vibrational modes associated with substitutional aluminium and nitrogen atoms in Al_{y} Ga_{1−y} N_{x} As_{1−x} have been studied within first-principles density functional theory using a supercell approach. Localized vibrational modes related to N-Al_{m} Ga_{4−m} (1⩽m⩽4) com...
[Phys. Rev. B 77, 155208] Published Wed Apr 16, 2008

Theory of conduction band structure of InN_{x} Sb_{1−x} and GaN_{x} Sb_{1−x} dilute nitride alloys

A. Lindsay, E. P. O’Reilly, A. D. Andreev, and T. Ashley — 2008-04-15T00:00:00-04:00

Author(s): A. Lindsay, E. P. O’Reilly, A. D. Andreev, and T. Ashley
The dependence of the optical band gap of InN_{x} Sb_{1−x} and GaN_{x} Sb_{1−x} on nitrogen content has been calculated using an sp^{3} s^{*} tight-binding Hamiltonian in large supercell calculations that explicitly include the effects of allowing a random distribution of nitrogen atoms. We calc...

[Phys. Rev. B 77, 165205] Published Tue Apr 15, 2008

Microstructure, magnetic, and spin-dependent transport properties of (Zn,Cr)Te films fabricated by magnetron sputtering

2008-04-15T00:00:00-04:00

Author(s): W. G. Wang, K. J. Yee, D. H. Kim, K. J. Han, X. R. Wang, C. Ni, T. Moriyama, A. Mathew, R. Opila, T. Zhu, and John Q. Xiao
Chromium doped zinc telluride thin films with various doping concentrations are fabricated by magnetron sputtering. These films are ferromagnetic and the Curie temperature increases with Cr concentration. X-ray diffraction, transmission electron microscopy, and magnetic circular dichroism characteri...
[Phys. Rev. B 77, 155207] Published Tue Apr 15, 2008

Ab initio supercell calculations on nitrogen-vacancy center in diamond: Electronic structure and hyperfine tensors

Adam Gali, Maria Fyta, and Efthimios Kaxiras — 2008-04-15T00:00:00-04:00

Author(s): Adam Gali, Maria Fyta, and Efthimios Kaxiras
The nitrogen-vacancy center in diamond is a promising candidate for realizing the spin qubits concept in quantum information. Even though this defect has been known for a long time, its electronic structure and other properties have not yet been explored in detail. We study the properties of the nit...

[Phys. Rev. B 77, 155206] Published Tue Apr 15, 2008

Ferromagnetic resonance of Ga_{0.93} Mn_{0.07} As thin films with constant Mn and variable free-hole concentrations

2008-04-11T00:00:00-04:00

Author(s): Kh. Khazen, H. J. von Bardeleben, J. L. Cantin, L. Thevenard, L. Largeau, O. Mauguin, and A. Lemaître
The magnetic properties of ferromagnetic Ga_{0.93} Mn_{0.07} As thin films have been investigated by X -band ferromagnetic resonance (FMR) spectroscopy as a function of hole concentration. The hole concentration [p] was varied from 10^{21} to<10^{18} cm^{−3} by hydrogen passivation. We determined the limit for the onset of ferromagnetism as [p]≈1×10^{19} cm^{−3} , the critical temperatures as a function of hole concentration, and the easy and hard axes for magnetization as a function of temperature and hole concentration. The temperature and hole concentration dependences of the magnetocrystalline anisotropy constants were determined. The dominant constant K_{2⊥} changes for T=4K from −8×10^{4} to+1×10^{4} erg∕cm^{3} with decreasing the hole concentration. The anisotropy coefficient κ_{2} varies with the reduced magnetization with an expected quadratic power law. The effective g factor is different from the paramagnetic value of Mn^{2+} of g=2.00 , due to the hole contribution; it changes from 1.90 to 1.97 with decreasing the hole concentration. In addition to the resonance positions, the FMR linewidth and intensity were analyzed. The FMR linewidth varies with the inverse of the hole concentration. Free energy surfaces are calculated for the simulation of magnetization switching.

[Phys. Rev. B 77, 165204] Published Fri Apr 11, 2008

Origin of the hot phonon effect in group-III nitrides

G. P. Srivastava — 2008-04-10T00:00:00-04:00

Author(s): G. P. Srivastava
Lifetimes of the zone-center A_{1} (LO) and higher- E_{2} modes in group-III-nitride wurtzite semiconductors have been calculated by employing a theoretical treatment of three-phonon and four-phonon processes based on realistic phonon dispersion curves and an elastic continuum model for crystal anha...
[Phys. Rev. B 77, 155205] Published Thu Apr 10, 2008

Point defects in pure amorphous silicon and their role in structural relaxation: A tight-binding molecular-dynamics study

Xavier Urli, Cristiano L. Dias, Laurent J. Lewis, and Sjoerd Roorda — 2008-04-09T00:00:00-04:00

Author(s): Xavier Urli, Cristiano L. Dias, Laurent J. Lewis, and Sjoerd Roorda
Structural relaxation in pure amorphous silicon (a-Si) produced by ion implantation has been attributed to the annihilation of point defects (vacancies and interstitials) introduced during the amorphization process. We have studied this problem by using tight-binding molecular-dynamics simulations. ...
[Phys. Rev. B 77, 155204] Published Wed Apr 09, 2008

Vibrational fine structures revealed by the real-time vibrational phase and amplitude in MEH-PPV using few cycle pulses

Jun Zhang, Zhuan Wang, and Takayoshi Kobayashi — 2008-04-09T00:00:00-04:00

Author(s): Jun Zhang, Zhuan Wang, and Takayoshi Kobayashi
It was found that the vibronic transition peaks hidden in a featureless spectrum of induced absorption could be clearly revealed by utilizing the spectra of phases and amplitudes of the molecular vibrational modes. Some of the peaks were also found in a second derivative of a transition spectrum int...
[Phys. Rev. B 77, 153202] Published Wed Apr 09, 2008

Vacuum-ultraviolet absorption of amorphous SiO_{2} : Intrinsic contribution and role of silanol groups

E. Vella, R. Boscaino, and G. Navarra — 2008-04-08T00:00:00-04:00

Author(s): E. Vella, R. Boscaino, and G. Navarra
We present a study on the vacuum-ultraviolet (VUV) absorption properties of amorphous SiO_{2} (a-SiO_{2} ) with high concentrations of silanol groups (Si-OH). We found that the absorption spectra are made up of a couple of exponential profiles. The first, in the range from ∼7.5 to ∼8.1 eV , wa...
[Phys. Rev. B 77, 165203] Published Tue Apr 08, 2008

Exciton spectroscopy of hexagonal boron nitride using nonresonant x-ray Raman scattering

2008-04-08T00:00:00-04:00

Author(s): Yejun Feng, J. A. Soininen, A. L. Ankudinov, J. O. Cross, G. T. Seidler, A. T. Macrander, J. J. Rehr, and E. L. Shirley
We report nonresonant x-ray Raman scattering (XRS) measurements on the boron K edge of hexagonal boron nitride for transferred momentum (q) from 2 to 9 Å^{−1} along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calcul...
[Phys. Rev. B 77, 165202] Published Tue Apr 08, 2008

Electronic structure of the nitrogen-vacancy center in diamond from first-principles theory

J. A. Larsson and P. Delaney — 2008-04-02T00:00:00-04:00

Author(s): J. A. Larsson and P. Delaney
The nitrogen-vacancy (NV) center is a paramagnetic defect in diamond with applications as a qubit. Here, we investigate its electronic structure by using ab initio density functional theory for five different NV center models of two different cluster sizes. We describe the symmetry and energetics of...
[Phys. Rev. B 77, 165201] Published Wed Apr 02, 2008

Planar Hall effect and uniaxial in-plane magnetic anisotropy in Mn δ -doped GaAs∕p-AlGaAs heterostructures

A. M. Nazmul, H. T. Lin, S. N. Tran, S. Ohya, and M. Tanaka — 2008-04-02T00:00:00-04:00

Author(s): A. M. Nazmul, H. T. Lin, S. N. Tran, S. Ohya, and M. Tanaka
We have studied the planar Hall effect (PHE) in a Mn δ -doped GaAs-based heterostructure consisting of Mn δ -doped GaAs and p -type AlGaAs. We observe a distinct and large PHE and a specific in-plane [110] uniaxial magnetic anisotropy below the ferromagnetic transition temperature (T_{C} ) . This ...
[Phys. Rev. B 77, 155203] Published Wed Apr 02, 2008

Density-functional study of bulk silicon lightly doped with manganese

Bhagawan R. Sahu, Sanjay K. Banerjee, and Leonard Kleinman — 2008-04-02T00:00:00-04:00

Author(s): Bhagawan R. Sahu, Sanjay K. Banerjee, and Leonard Kleinman
With only a 0.8% concentration of Mn impurities, Si has been found to be ferromagnetic up to well above 400K . Using the generalized gradient approximation, both with and without a Hubbard U , for exchange and correlation, we have calculated the properties of a 250 atom Si supercell with two Mn impu...
[Phys. Rev. B 77, 155202] Published Wed Apr 02, 2008

First-principles study of transition metal impurities in Si

Z. Z. Zhang, B. Partoens, Kai Chang, and F. M. Peeters — 2008-04-02T00:00:00-04:00

Author(s): Z. Z. Zhang, B. Partoens, Kai Chang, and F. M. Peeters
By using ab initio electronic structure calculations within density functional theory, we study the structural, electronic, and magnetic properties of Si doped with a transition metal impurity. We consider the transition metals of the 3d series V, Cr, Mn, Fe, Co, and Ni. To get insight into the leve...
[Phys. Rev. B 77, 155201] Published Wed Apr 02, 2008

Ab initio studies of structural and electronic properties of the crystalline Ge_{2} Sb_{2} Te_{5}

Geunsik Lee and Seung-Hoon Jhi — 2008-04-02T00:00:00-04:00

Author(s): Geunsik Lee and Seung-Hoon Jhi
We study the atomic structure and the electronic and optical properties of Ge_{2} Sb_{2} Te_{5} in two different crystalline states of cubic and hexagonal structures with the use of ab initio pseudopotential density functional method. It is found that electronic and atomic structures are very sensit...
[Phys. Rev. B 77, 153201] Published Wed Apr 02, 2008

Infrared single-photon detection by two-photon absorption in silicon

Alex Hayat, Pavel Ginzburg, and Meir Orenstein — 2008-03-31T00:00:00-04:00

Author(s): Alex Hayat, Pavel Ginzburg, and Meir Orenstein
We propose a scheme for infrared single-photon detection based on two-photon absorption at room temperature in Si avalanche photodiodes, where the detected photon’s energy is lower than the band gap and the energy difference is complemented by a pump field. A quantum nonperturbative model is devel...
[Phys. Rev. B 77, 125219] Published Mon Mar 31, 2008

Temperature dependence of the optical response: Application to bulk GaAs using first-principles molecular dynamics simulations

2008-03-28T00:00:00-04:00

Author(s): Z. A. Ibrahim, A. I. Shkrebtii, M. J. Lee, K. Vynck, T. Teatro, W. Richter, T. Trepk, and T. Zettler
We present an approach that takes into account lattice dynamical effects in calculating the optical response of semiconductors by averaging over several perturbed configurations of a supercell extracted from molecular dynamic simulations. The validity of this approach is confirmed by comparing our r...
[Phys. Rev. B 77, 125218] Published Fri Mar 28, 2008

Pressure-induced structural changes in liquid cadmium telluride: Ab initio molecular dynamics study

Yasuhisa Miyata, Fuyuki Shimojo, and Masaru Aniya — 2008-03-28T00:00:00-04:00

Author(s): Yasuhisa Miyata, Fuyuki Shimojo, and Masaru Aniya
The structural and electronic properties of liquid CdTe under pressure are studied by ab initio molecular dynamics simulations. It is shown that the pressure dependence of the static structure factor observed by the recent x-ray-diffraction experiments is successfully reproduced by our simulations f...
[Phys. Rev. B 77, 125217] Published Fri Mar 28, 2008

General mobility and carrier concentration relationship in transparent amorphous indium zinc oxide films

2008-03-28T00:00:00-04:00

Author(s): Andrew J. Leenheer, John D. Perkins, Maikel F. van Hest, Joseph J. Berry, Ryan P. O’Hayre, and David S. Ginley
We report the dependence of the electronic properties on the metal composition and oxygen content of transparent conducting amorphous indium zinc oxide (a-IZO) films deposited by dc magnetron sputtering. a-IZO shows a clear Burstein–Moss shift with an effective optical band gap of 3.1eV independen...
[Phys. Rev. B 77, 115215] Published Fri Mar 28, 2008