Control of Ordering-Disordering Defect Parameters for the Realization of Efficient Opto-Electronic Devices

1992 ◽  
Vol 262 ◽  
Author(s):  
J. P. André ◽  
P. Bellon
Keyword(s):  
Band Gap ◽  
Growth Parameters ◽  
Growth Models ◽  
Electronic Devices ◽  
Optoelectronic Devices ◽  
Band Gap Energy ◽  
Laser Application ◽  
High Quality ◽  
Band Gap Engineering ◽  
Gap Energy

ABSTRACTEpitaxial growth of III/V compounds with tight band gap engineering is essential for the realization of efficient optoelectronic devices. Using MOVPE, high quality materials have been grown with anomalous low band gap energy. The order/disorder phenomena and their relation to the band gap energy in the GalnP/AlGalnP system are reported. The effect of the growth parameters on the ordered phase and the band gap Eg will be presented by using TEM and PL characterizations. The growth models will be discussed. The importance of the ordering phenomena will be illustrated by short wavelength laser application, the emission wavelength being as low as 650 ran at 300 K. And a possible future laser structure will be proposed.

Temperature Dependence Of The Fundamental Band Gap In Hexagonal GaN

1997 ◽  
Vol 482 ◽  
Author(s):  
H. Herr ◽  
V. Alex ◽  
J. Weber
Keyword(s):  
Temperature Dependence ◽  
Band Gap ◽  
Line Shape ◽  
Free Exciton ◽  
Band Gap Energy ◽  
Recombination Process ◽  
Photoluminescence Spectra ◽  
High Quality ◽  
Fundamental Band ◽  
Gap Energy

AbstractPhotoluminescence spectra of hexagonal GaN were measured in the temperature range T= 2 – 1200 K. We identify the Free Exciton (FX) as the dominant recombination process in our high quality samples for temperatures above 200 K. From the line shape fit of the FX we determine the excitonic band gap shift with temperature. An analysis according to the empirical Varshni equation gives Eg (T)-Eg(0 K) = (-α T2)/(T + β), with α = (7.3 ± 0.3)·10−4 eV/K and β = (594 ± 54) K. We have detected significant differences in the band gap energy at low and higher temperatures for GaN layers grown on different substrate materials. Heating GaN above 1200 K leads to irreversible changes in the near band gap photoluminescence spectra.

scholarly journals Ligand & band gap engineering: tailoring the protocol synthesis for achieving high-quality CsPbI3 quantum dots

Nanoscale ◽  
2020 ◽  
Vol 12 (26) ◽  
pp. 14194-14203 ◽  
Author(s):  
Ehsan Hassanabadi ◽  
Masoud Latifi ◽  
Andrés. F. Gualdrón-Reyes ◽  
Sofia Masi ◽  
Seog Joon Yoon ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Optoelectronic Devices ◽  
High Quality ◽  
Band Gap Engineering ◽  
Hot Injection ◽  
Perovskite Quantum Dots

Hot-injection has become the most widespread method used for the synthesis of perovskite quantum dots (QDs) with enormous interest for application in optoelectronic devices.

Band-GaP Energy and Physical Properties of InN Grown by RF-Molecular Beam Epitaxy

2003 ◽  
Vol 798 ◽  
Author(s):  
Yasushi Nanishi ◽  
Yoshiki Saito ◽  
Tomohiro Yamaguchi ◽  
Fumie Matsuda ◽  
Tsutomu Araki ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Band Gap ◽  
Hexagonal Wurtzite Structure ◽  
Band Gap Energy ◽  
High Quality ◽  
Precise Control ◽  
Gap Energy ◽  
Optimum Growth Temperature ◽  
Si Substrates ◽  
Aln Buffer

ABSTRACTThis paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films were investigated and (1) nitridation process of sapphire substrates prior to growth, (2) precise control of V/III ratio and (3) selection of optimum growth temperature were found to be essential. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films obtained in this study have ideal hexagonal wurtzite structure. FWHMs of ω-2Θ mode XRD and E2(high)-phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm-1, respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN grown in this study. PbS, instead of InGaAs, was used as a detector for PL study in order to solve the problem coming from the cut-off wavelength of InGaAs detector. Based on these systematic studies on structural and optical property characterizations using high-quality InN, true band-gap energy of InN is suggested to be less than 0.67 eV and approximately 0.65 eV at room temperature. Single-crystalline InN films are also successfully grown on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

Stability Investigation in the Optical Properties of Thermally Evaporated Ge5Se95-x Znx Thin Films

2015 ◽  
Vol 7 (3) ◽  
pp. 1923-1930
Author(s):  
Austine Amukayia Mulama ◽  
Julius Mwakondo Mwabora ◽  
Andrew Odhiambo Oduor ◽  
Cosmas Mulwa Muiva ◽  
Boniface Muthoka ◽  
...  
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Optical Band Gap ◽  
Thermal Evaporation ◽  
Optical Transition ◽  
Bulk Material ◽  
Band Gap Energy ◽  
Optical Absorbance ◽  
Gap Energy ◽  
Constituent Elements

 Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ≤ x ≤ 4 at.%) has been prepared from high purity constituent elements. Thin films from the bulk material were deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as-deposited thin films using transmission spectra. The allowed optical transition was found to be indirect and the corresponding band gap energy determined. The variation of optical band gap energy with the average coordination number has also been investigated based on the chemical bonding between the constituents and the rigidity behaviour of the system’s network.

scholarly journals Polymer Thermal Treatment Production of Cerium Doped Willemite Nanoparticles: An Analysis of Structure, Energy Band Gap and Luminescence Properties

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1118
Author(s):  
Ibrahim Mustapha Alibe ◽  
Khamirul Amin Matori ◽  
Mohd Hafiz Mohd Zaid ◽  
Salisu Nasir ◽  
Ali Mustapha Alibe ◽  
...  
Keyword(s):  
Solid State ◽  
Thermal Treatment ◽  
Band Gap ◽  
Optical Band Gap ◽  
Dopant Concentration ◽  
Blue Emission ◽  
Green Emission ◽  
Band Gap Energy ◽  
Solid State Lighting ◽  
Gap Energy

The contemporary market needs for enhanced solid–state lighting devices has led to an increased demand for the production of willemite based phosphors using low-cost techniques. In this study, Ce3+ doped willemite nanoparticles were fabricated using polymer thermal treatment method. The special effects of the calcination temperatures and the dopant concentration on the structural and optical properties of the material were thoroughly studied. The XRD analysis of the samples treated at 900 °C revealed the development and or materialization of the willemite phase. The increase in the dopant concentration causes an expansion of the lattice owing to the replacement of larger Ce3+ ions for smaller Zn2+ ions. Based on the FESEM and TEM micrographs, the nanoparticles size increases with the increase in the cerium ions. The mean particles sizes were estimated to be 23.61 nm at 1 mol% to 34.02 nm at 5 mol% of the cerium dopant. The optical band gap energy of the doped samples formed at 900 °C decreased precisely by 0.21 eV (i.e., 5.21 to 5.00 eV). The PL analysis of the doped samples exhibits a strong emission at 400 nm which is ascribed to the transition of an electron from localized Ce2f state to the valence band of O2p. The energy level of the Ce3+ ions affects the willemite crystal lattice, thus causing a decrease in the intensity of the green emission at 530 nm and the blue emission at 485 nm. The wide optical band gap energy of the willemite produced is expected to pave the way for exciting innovations in solid–state lighting applications.

Phase transformation and heterojunction construction of bismuth oxyiodides by grinding-assistant calcination in the presence of thiourea and its photoactivity

2021 ◽  
Author(s):  
Zichen Shen ◽  
Huanzhen Liu ◽  
Xuemei Jia ◽  
Qiaofeng Han ◽  
Huiping Bi
Keyword(s):  
Phase Transformation ◽  
Band Gap ◽  
Layered Structure ◽  
Band Gap Energy ◽  
Gap Energy

Bismuth-rich oxyhalides are promising photocatalysts due to their special layered structure and adjustable band gap energy. In this work, a series of bismuth oxyiodides were fabricated by grinding-assistant calcining in...

Quantum confinement effects and strain-induced band-gap energy shifts in core-shell Si-SiO2nanowires

2011 ◽  
Vol 83 (24) ◽  
Author(s):  
O. Demichel ◽  
V. Calvo ◽  
P. Noé ◽  
B. Salem ◽  
P.-F. Fazzini ◽  
...  
Keyword(s):  
Band Gap ◽  
Quantum Confinement ◽  
Band Gap Energy ◽  
Core Shell ◽  
Confinement Effects ◽  
Gap Energy ◽  
Quantum Confinement Effects
Sign in / Sign up

Export Citation Format

Share Document