Search results

1

Photoreflectance Measurements of InGaAs/GaAs Quantum Wells

100%

Tomaszewicz T., Korona K., Bożek R., Baranowski J.

Acta Physica Polonica A

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1996

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vol. 90

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issue 5

965-968

EN

Samples with InGaAs/GaAs quantum wells were grown by metallo-organic chemical vapour deposition in order to detect and analyze GaSb islands deposited on the surface. Results of photoreflectance measurements of quantum wells are reported. The correspondence between broadening of quantum well transition lines and GaSb structures has been observed.

2

Deep Level Transient Spectroscopic Studies of MOCVD GaN Layers Grown on Sapphire

100%

Śliwiński A., Korona K., Pakuła K., Baranowski J.

Acta Physica Polonica A

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1996

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vol. 90

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issue 5

955-958

EN

The deep level transient spectroscopy of GaN heteroepitaxial layers grown on sapphire was studied. The samples were Mg doped during the growth. The as-grown material is n-type. It becomes p-type after annealing. The samples were measured in the temperature range from 77 K to 420 K. In n-type GaN, one peak (EG1) with activation energy 0.75 eV was detected. In p-type, at least three peaks were observed: AS1 at temperature about 300 K and AS2, AS3 at about 400 K. The dominating one is AS3. It has an activation energy about 1.1 eV.

3

Efficient Emission from InAlGaAs Single Quantum Dots with Low Lattice Misfit and AlGaAs Indirect Bandgap Barrier

100%

Słupiński T., Korona K., Papierska J., Borysiuk J.

Acta Physica Polonica A

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2016

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vol. 130

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issue 5

1229-1232

EN

We report on molecular beam epitaxy growth and properties of rarely studied quaternary In_{0.4}(Al_{0.75}Ga_{0.25})_{0.6}As self-assembled quantum dots, which show strong and efficient emission of red light from single quantum dots. The increased yield is, among others, due to efficient energy transfer from indirect band-gap Al_{0.75}Ga_{0.25}As barriers. To maximize photon energy emitted from quantum dots, low In composition, x_{In} = 0.4 was applied, which also lowered the lattice misfit close to the limit of 2D/3D transition in the Stranski-Krastanov growth mode. Time-resolved micro-photoluminescence shows emission at 650-750 nm. Well-resolved single quantum dot photoluminescence lines (decay time of ≈ 1-2 ns) are observed despite a high concentration ≈ 3×10¹¹ cm¯² of quantum dots. We discuss this observation assuming newly a role of carriers or excitons diffusion/tunneling between quantum dots at high surface concentration of dots and a possible role of lattice disorder inside the dot on the exciton lifetime.

4

Deep Defects in Low-Temperature GaAs

100%

Korona K., Muszalski J., Kamińska M., Weber E.

Acta Physica Polonica A

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1992

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vol. 82

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issue 5

821-824

EN

Conductivity of GaAs layers grown by molecular beam epitaxy at low substrate temperature (190-200°C) and then annealed at few different temperatures (between 300 and 600°C) were studied. It was confirmed that electron transport is due to hopping between arsenic antisite defects. Parameters describing hopping conductivity and their dependence on temperature of annealing are discussed. Other deep defects with activation energies of 0.105, 0.30, 0.31, 0.47, 0.55 eV were found using photoinduced current transient spectroscopy measurements.

5

Model of Hopping between Deep Centers in Low Temperature GaAs

100%

Korona K., Kamińska M., Baranowski J.

Acta Physica Polonica A

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1995

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vol. 87

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issue 2

337-340

EN

A model explaining hopping conductivity via EL2 deep centers in low temperature GaAs is presented. It is proposed that the wave function of the EL2 center consists of a localized part and of an external one. The model can describe such features as large wave function radius of hopping centers, changes of the conductivity during transition of EL2 to the metastable state and a high potential fluctuation amplitude.

6

Influence of Electric Field on Recombination Dynamics of Quantum Confined Carriers

100%

Korona K., Borysiuk J., Skierbiszewski C., Porowski S.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

243-247

EN

We present time-resolved photoluminescence measurements of GaN/AlGaN low dimensional structures showing very characteristic changes of dynamics related to strong electric field. Strong piezoelectric and spontaneous polarizations built-in in nitride structures lead to the changes in spatial separation of carriers which leads to changes in recombination energies and radiative lifetimes of the carriers. The observed effect can be well described by a simple exponential relation. The observed dependence can be explained by an approximated model of quantum-confined Stark effect based on the Airy functions.

7

Multiband GaN/AlGaN UV Photodetector

100%

Korona K., Drabińska A., Pakuła K., Baranowski J.

Acta Physica Polonica A

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2006

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vol. 110

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issue 2

211-217

EN

We present optical and electrical measurements made on GaN/AlGaN photodetector structure capable to detect three UV ranges, tuned by external voltage. The highest band at energy of about 3.85 eV is nearly independent of bias applied to the Schottky contact. Photosensitivity of the second band at about 3.65 eV changes strongly with the bias. Signal in this range increases about 20 times when the bias changes from 0 V to -4 V. Photosensitivity of the third band (3.4 eV) appears for strong reverse bias (-3 V). Characteristics of the detector are in qualitative agreement with numerical model, however deep centers present in the AlGaN layers cause quantitative discrepancies. The concentration of defects of the order of 10^{16} cm^{-3} was estimated from current transients.

8

Dynamics of Excitation Transfer Inside InAs/GaAs Quantum Dot System

100%

Korona K., Babiński A., Raymond S., Wasilewski Z.

Acta Physica Polonica A

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2006

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vol. 110

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issue 2

219-224

EN

We present time-resolved photoluminescence investigations of InAs/GaAs structures containing quantum dots with the ground state at 1.43 eV. State filling effect and a Pauli blocking effect were clearly observed. These effects significantly influenced dynamics of excitation transfer from upper to lower state inside a dot leading to non-exponential dynamics. Numerical model based on nonlinear rate equations was proposed. The model described well the experimental data providing values of: lifetime of the ground state 0.53±0.03 ns, lifetime of excited state (when the ground state is full) 1.1±0.2 ns, and internal relaxation time (when the ground state is empty) 0.07±0.01 ns.

9

Dynamics of Photoexcited Carriers in GaInAs/GaAs Quantum Dots

100%

Ilczuk E., Korona K., Babiński A., Kuhl J.

Acta Physica Polonica A

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2001

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vol. 100

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issue 3

379-386

EN

We present photocurrent and time-resolved photoluminescence investigations of AlGaAs/GaInAs/GaAs structures containing GaInAs/GaAs self-assembled quantum dots. The high electrical field in those devices significantly influences carrier dynamics. The photocurrent spectra show a double peak with maxima at 1.40 and 1.47 eV (at 80 K). These maxima are due to the GaInAs wetting layer (higher) and the quantum dots (lower). The photoluminescence spectra comprise weak excitonic luminescence from GaAs at 1.504 eV (at 80 K) and stronger and broad emission from the Ga_{0.4}In_{0.6}As quantum dots. At 300 K, the quantum dots emission has a lifetime of 1.1 ns and has a maximum at an energy of 1.38 eV. By analysis of both experiments, we can separate the influence of different radiative and nonradiative recombination processes. So, the tunneling rate: r_T=0.5 ns^{-1} and the radiative recombination rate in the quantum dots: r_{RQD}=0.4 ns^{-1} have been determined. The high tunneling probability (due to the influence of the built-in electric field) reveals that the tunneling effect is important for the recombination and transport processes in our structures.

10

Transport of Photoexcited Electron-Hole Plasma in GaN/AlGaN Quantum Well

100%

Korona K., Caban P., Strupiński W.

Acta Physica Polonica A

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2009

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vol. 116

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issue 5

927-929

EN

We report spatially resolved photocurrent measurements showing transport of excitation on long distances in plane of a 6 nm GaN/Al_{0.1}Ga_{0.9}N quantum well. The strong field present in nitrides (due to large spontaneous and piezoelectric polarizations) leads to lower recombination rates of electrons and holes, so in the case of electron-hole pairs excited by light, relatively long-lived electron-hole plasma could be generated. In the case of the investigated quantum well, lifetime of few μs was expected. The thermal measurements showed that barriers were low enough, so all excited carriers could reach the electrode (thermal activation energy of 0.11 eV was found). The diffusion length for unbiased structure was about 40 μm. It was observed that the charge transport could be clearly accelerated by bias. In the biased quantum well, the transport range was of the order of 100 μm under both positive and negative bias. The reported effect of long transport range is very important for electronic devices made on the GaN/AlGaN structures.

11

Tuning of Spectral Sensitivity of AlGaN/GaN UV Detector

76%

Korona K., Drabińska A., Trajnerowicz A., Bożek R., Pakuła K., Baranowski J.

Acta Physica Polonica A

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2003

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vol. 103

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issue 6

675-681

EN

GaN/AlGaN photodetector that exhibits new interesting property is presented. Its spectral sensitivity depends upon bias voltage. Under positive or low negative bias the detector is sensitive mainly to the ultrafiolet radiation absorbed by AlGaN layer 3.7-3.8 eV. Under negative bias U_B below -4 V, the detector is sensitive mainly to the radiation absorbed by GaN (3.4-3.6 eV). The effect can be explained based on numerical calculations of the electric field and potential profiles of this structure. The damping of GaN signal is attributed to activity of 2D electron gas formed on the GaN/AlGaN interface by spontaneous polarization. The reappearing of the signal is attributed to tunneling of holes through AlGaN, stimulated by a high electric field.

12

A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

76%

Dróżdż P., Korona K., Sarzyński M., Czernecki R., Skierbiszewski C., Muzioł G., Suski T.

Acta Physica Polonica A

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2016

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vol. 130

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issue 5

1209-1212

EN

The potential fluctuations in III-nitride quantum wells lead to many effects like emission broadening and S-shape energy vs. temperature dependence. The best description of the energy dependence comes from calculations based on Gaussian density of states. However, in most of the published reports, changes of carrier lifetime with energy and temperature are not taken into account. Since experimental evidence shows that lifetime significantly depends on energy and temperature, here we propose a model that describes two basic parameters of luminescence: lifetime of carries and emission energy as a function of temperature in the case of quantum wells and layers that are characterized by potential fluctuations. Comparison of the measured energy and lifetime dependences on temperature in specially grown InGaN/GaN quantum wells and InAlGaN layer shows very good agreement with the proposed theoretical approach.

13

Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

76%

Binder J., Korona K., Borysiuk J., Wysmołek A., Baeumler M., Köhler K., Kirste L.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

918-920

EN

In this work we present measurements of GaInN/GaN light emitting diodes (LEDs) with an active layer consisting of three quantum wells made of Ga_{0.9}In_{0.10}N that have different widths (1.8 nm, 2.7 nm, 3.7 nm). A comparison of emission and absorption (photocurrent) on the same sample revealed a shift in energy, with the emission energy being significantly lower. The shifts are about 0.02 eV, 0.03 eV, and 0.04 eV for the quantum wells having the widths of 1.8 nm, 2.7 nm, and 3.7 nm, respectively. This can be explained by a shift of the ground state energy caused by the quantum confined Stark effect. Calculations show that due to the spontaneous polarization and the piezoelectric effect a strong electric field of the order of 1 MV/cm was present in the GaInN quantum wells. Simulations of ground-state energies in the model of an infinite square well under the influence of an electric field with a matched effective well width were performed and used to interpret the experimental results.

14

FFirst TSC and DLTS Measurements of Low Temperature GaAs

76%

Muszalski J., Babiński A., Korona K., Kamińska E., Piotrowska A., Kamińska M., Weber E.

Acta Physica Polonica A

|

1991

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vol. 80

|

issue 3

413-416

EN

The first thermally stimulated current (TSC) and deep level transient spectroscopy (DLTS) studies performed on GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures (LT GaAs) are reported. TSC experiments, conducted on as grown and 400-580°C annealed layers showed domination of arsenic antisite (EL2-like) defect and supported its key role in hopping conductivity. DLTS studies, performed on Si doped and annealed at 800°C layers revealed substantially lower concentration of EL2-like defect and an electron trap of activation energy ΔE = 0.38 eV was found.

15

Defects Studies in As Grown and Neutron Irradiatcd Phosphorus Rich GaP

76%

Jasiński J., Palczewska M., Korona K., Kamińska M., Bourret E., Elliot G.

Acta Physica Polonica A

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1992

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vol. 82

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issue 5

829-832

EN

Semi-insulating, p- and n-type liquid encapsulated Czochralski grown phosphorus rich GaP crystals before and alter neutron irradiation were studied. EPR measurements proved that the phosphorus antisite defect P_{Ga} introduced by neutron irradiation was exactly the same as in as grown materials, i.e. surrounded by four substitutional phosphorus atoms. In neutron irradiated crystals EPR showed also a signal, similar to the one found in plastically deformed GaAs and GaP. The concentrations of P_{Ga} and of the other defect were estimated to be of the same order of magnitude. Two absorption bands at 0.81 and 1.12 eV were found for irradiated materials. The temperature dependence of resistivity indicated hopping as the mechanism of conduction in samples irradiated with doses higher than 4 × 10^{16} cm^{-2}.

16

Anharmonic Optical Phonon Effects in ZnO Nanocrystals

76%

Khusnutdinov S., Dynowska E., Zaleszczyk W., Makhniy V., Wysmołek A., Korona K.

Acta Physica Polonica A

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2011

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vol. 119

|

issue 5

678-680

EN

Zinc oxide (ZnO) is a very promising material for optoelectrical devices operating at the short-wavelength end of the visible spectral range and at the near UV. The Raman scattering studies of ZnO heterolayers formed by isothermal annealing show sharp phonon lines. In addition to the A_1(TO), E_1(TO), E_2^{H}, and E_1(LO) one-phonon lines, we observed two-phonon lines identified as: E_2^{H} - E_2^{L}, E_2^{H} + E_2^{L}, and 2LO at 332, 541, and 1160 cm^{-1}, respectively (at room temperature). The identification of the E_2^{H} - E_2^{L} peak was confirmed by its thermal dependence. Temperature dependent measurements in the range 6-300 K show that the phonon frequencies decrease with temperature. The E_2^{H} peak is at energy 54.44 meV (439.1 cm^{-1}), at 4 K and due to phonon-phonon anharmonic interaction, its energy decreases to 54.33 meV (438.2 cm^{-1}) at room temperature. The Grüneisen parameter found for this oscillation mode was γ_{E} 2H = 1.1 at about 300 K. The intensity of the E_2^{H} - E_2^{L} peak increases strongly with temperature and this dependence can be described by the Bose-Einstein statistics with activation energy of 13.8 meV (nearly equal to the energy of the E_2^{L} phonon).

17

Optical and Electrical Measurements of Low-Temperature InAlAs

76%

Korona K., Wysmołek A., Bożek R., Kamińska M., Baranowski J., Weber E.

Acta Physica Polonica A

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1992

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vol. 82

|

issue 5

825-828

EN

Photoluminescence, photocurrent, thermally stimulated current and photoinduced current transient spectroscopy measurements done on molecular beam epitaxy In_{0.52}Al_{0.48}As layer, lattice matched to InP are reported. The investigated layers were grown on semi-insulating InP wafers, at temperature range from 215 to 450°C. It was found that the Fermi level was pinned to a dominant midgap center (most likely similar to EL2 center). Moreover, there were at least 7 other defects but with much smaller concentrations. Their activation energies were equal to 0.076, 0.11, 0.185, 0.295, 0.32 and 0.40 eV. The layers exhibited a very low luminescence and a small photocurrent.

18

Optical and Electrical Studies of FR1 and FR2 Defects in GaAs

76%

Dwiliński R., Palczewska M., Kaczor P., Korona K., Wysmołek A., Bożek R., Kamińska M.

Acta Physica Polonica A

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1992

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vol. 82

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issue 4

613-616

EN

The systematic EPR, optical absorption, photoluminescence and thermally stimulated current studies of acceptor defects in bulk GaAs were performed. For the first time, parallel EPR and optical absorption experiments allowed to find the absorption spectrum due to the photoionization of FR1 defect with the threshold at 0.19 eV. Photoluminescence studies showed two families of bands in the energy range of about 1.25 to 1.35 eV. We tentatively ascribed them to FR1 and FR2 complexes with shallow donors. Thermally stimulated current measurements showed two peaks at 90 K and 110 K assigned to FR1 and FR2 respectively.

19

Photoluminescence Dynamics of GaN/Si Nanowires

76%

Korona K., Zytkiewicz Z., Perkowska P., Borysiuk J., Binder J., Sobanska M., Klosek K.

Acta Physica Polonica A

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2012

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vol. 122

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issue 6

1001-1003

EN

In this work we present analysis of carriers dynamics in samples of GaN nanowires grown on silicon. The samples exhibit bright luminescence of bulk donor-bound excitons at 3.472 eV, surface defect-bound excitons at 3.450 eV (SDX) and a broad (0.05 eV) band centered at 3.47 eV caused probably by single free exciton and bi-exciton recombination. The SDX emission has long lifetime τ = 0.6 ns at 4 K and can be observed up to 50 K. At higher temperatures luminescence is dominated by free excitons. The broad excitonic band is best visible under high excitation, and reveals fast, non-exponential dynamics. We present mathematical model assuming exciton-exciton interaction leading to the Auger processes. The model includes n^2 (Langevin) term and describes well the non-exponential dynamics of the excitonic band.

20

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials

76%

Ziółkowska D., Korona K., Kamińska M., Grzanka E., Andrzejczuk M., Wu S., Chen M.

Acta Physica Polonica A

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2011

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vol. 120

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issue 5

973-975

EN

Structure of samples of lithium iron vanadium phosphates of different compositions were investigated by X-rays, electron microscopy and Raman spectroscopy. The investigated salts were mainly of olivine-like and NASICON-like structures. The X-ray diffraction and the Raman scattering show different crystalline structures, which is probably caused by difference between cores of the crystallites (probed by X-rays) and their shells (probed by the Raman scattering). Most of the Raman spectra were identified with previously published data, however in the samples with high vanadium concentration we have observed new, not reported earlier modes at 835 cm^{-1} and 877 cm^{-1}, that we identified as oscillations related to V_2O_7^{4-} or VO_4^{3-} anions.

Refine search results

Photoreflectance Measurements of InGaAs/GaAs Quantum Wells

Deep Level Transient Spectroscopic Studies of MOCVD GaN Layers Grown on Sapphire

Efficient Emission from InAlGaAs Single Quantum Dots with Low Lattice Misfit and AlGaAs Indirect Bandgap Barrier

Deep Defects in Low-Temperature GaAs

Model of Hopping between Deep Centers in Low Temperature GaAs

Influence of Electric Field on Recombination Dynamics of Quantum Confined Carriers

Multiband GaN/AlGaN UV Photodetector

Dynamics of Excitation Transfer Inside InAs/GaAs Quantum Dot System

Dynamics of Photoexcited Carriers in GaInAs/GaAs Quantum Dots

Transport of Photoexcited Electron-Hole Plasma in GaN/AlGaN Quantum Well

Tuning of Spectral Sensitivity of AlGaN/GaN UV Detector

A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

FFirst TSC and DLTS Measurements of Low Temperature GaAs

Defects Studies in As Grown and Neutron Irradiatcd Phosphorus Rich GaP

Anharmonic Optical Phonon Effects in ZnO Nanocrystals

Optical and Electrical Measurements of Low-Temperature InAlAs

Optical and Electrical Studies of FR1 and FR2 Defects in GaAs

Photoluminescence Dynamics of GaN/Si Nanowires

Raman Spectroscopy of LiFePO_4 and Li_3V_2(PO_4)_3 Prepared as Cathode Materials