Optical Properties of Doped Cd1−xMnxTe

1986 ◽  
Vol 89 ◽  
Author(s):  
Y. Lansari ◽  
N. C. Giles ◽  
J. F. Schetzina ◽  
P. Becia ◽  
D. Kaiser
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Spectral Range ◽  
Room Temperature ◽  
Far Infrared ◽  
Optical Quality ◽  
Structural Quality ◽  
Reflectance Measurements ◽  
Low Temperature Photoluminescence

AbstractThe introduction of phosphorus and arsenic dopants into bulk Cd1−xMnx Te crystals grown by the Bridgman-Stockbarger technique has been studieA-with respect to the resulting optical properties. Samples with a Mn composition in the range 0.10 < x < 0.30, both as-grown and annealed, were investigated. A combination of room temperature transmittance and reflectance measurements over the spectral range from the ultraviolet to the far infrared has been used to gain information concerning the structural quality of the samples. Low temperature photoluminescence measurements (1.6−5 K) were used to determine optical quality and excitonic energies.

Electrical resistivity and photoluminescence of lead iodide crystals

2007 ◽  
Vol 61 (1) ◽  
Author(s):  
M. Matuchová ◽  
K. Žďánský ◽  
M. Svatuška ◽  
J. Zavadil ◽  
O. Procházková
Keyword(s):  
Electrical Resistivity ◽  
Optical Properties ◽  
Room Temperature ◽  
Direct Synthesis ◽  
Zone Melting ◽  
Lead Iodide ◽  
Electrical And Optical Properties ◽  
X Ray ◽  
Low Temperature Photoluminescence

AbstractDirect synthesis of lead iodide, a promising material for X-ray and γ detectors operating at room temperature, was developed and optimized. The influence of admixture of rare earth elements Ce, Ho, Gd, Yb, Er, and Tb in concentrations 0.05–0.5 at. % on the quality of prepared PbI2 was investigated. Zone melting was employed in order to increase the lead iodide purity. Electrical and optical properties of PbI2 samples were assessed on the basis of the measurement of electrical resistivity and low-temperature photoluminescence. The electrical resistivity of synthesized samples varied from 109 Ω cm to 1011 Ω cm and occasionally it was increased up to 1013 Ω cm.

OPTICAL PROPERTIES OF CdTe/ZnTe ULTRATHIN QUANTUM WELLS GROWN BY ATOMIC LAYER EPITAXY

2002 ◽  
Vol 09 (05n06) ◽  
pp. 1667-1670 ◽  
Author(s):  
M. GARCÍA-ROCHA ◽  
I. HERNÁNDEZ-CALDERÓN
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Quantum Wells ◽  
Gaas Substrate ◽  
Room Temperature ◽  
Diffusion Length ◽  
Substrate Surface ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Low Temperature Photoluminescence

Ultrathin quantum wells (UTQWs) of CdTe within ZnTe barriers were successfully grown by atomic layer epitaxy (ALE) on GaAs(001) substrates. ALE growth of CdTe was performed by alternate exposure of the substrate surface to individual fluxes of Cd and Te. Two different samples with 2-monolayer (ML) (substrate temperature Ts= 270° C ) and 4 ML (Ts = 290° C ) CdTe QWs were grown. Low temperature photoluminescence (PL) experiments exhibited intense and sharp peaks associated to the 2 ML QWs at 2.26 eV. In the case of the nominally 4-ML-thick QW the PL spectrum presented an intense peak around 2.13 eV and two weak features around 2.04 and 1.91 eV. The first peak is attributed to ~ 3 ML QW and the second one to ~ 4 ML QW. The dominance of the 3 ML peak is mainly attributed to Cd loss in the QW due to its substitution by Zn atoms. Due to a high diffusion length of the photogenerated carriers in the barriers, quite weak signals from the ZnTe barriers were observed in both cases. Room temperature (RT) photoreflectance (PR) spectra showed contributions from the CdTe UTQWs, the ZnTe barriers, and the GaAs substrate.

Optical Properties of Mg-GaN, GaN/AlGaN SCH structures, and GaN on ZnO Substrates

1995 ◽  
Vol 395 ◽  
Author(s):  
H. Morkoç ◽  
W. Kim ◽  
Ö. Aktas ◽  
A. Salvador ◽  
A. Botchkarev ◽  
...  
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Room Temperature ◽  
Stimulated Emission ◽  
Lattice Match ◽  
Photoluminescence Emission ◽  
Stacking Order ◽  
Near Ultraviolet ◽  
Side Pumping ◽  
Low Temperature Photoluminescence

ABSTRACTGaN films and GaN/AlGaN heterostructures have been gro wn by MBE. GaN films doped with varying levels of Mg indicate effective mass acceptor at low doping concentrations, as determined from strong photoluminescence emission at about 380 nm. As the Mg concentration is increased the photoluminescence emission line red shifts considerably, indicating the formation of Mg-related or induced complexes whose lifetimes are relatively short. GaN/AlGaN separate confinement heterostructures grown on sapphire show strong near ultraviolet stimulated emission at room temperature in a side-pumping configuration. The pumping threshold for stimulated emission at room temperature was found to be ∼90 kW/cm2. Initial GaN films grown on ZnO substrates show the A exciton in low temperature photoluminescence. ZnO is being considered for nitride growth because of its stacking order and close lattice match.

scholarly journals Postharvest quality of pepino melon (Solanum muricatum Aiton) as influenced by NPK fertilizer rates, growing environment and storage temperature

2021 ◽  
Vol 35 (1) ◽  
Author(s):  
Carol Mutua ◽  
Joshua Ogweno ◽  
Robert Gesimba
Keyword(s):  
Low Temperature ◽  
Shelf Life ◽  
Room Temperature ◽  
Postharvest Quality ◽  
Solanum Muricatum ◽  
Npk Fertilizer ◽  
And Storage ◽  
Fertilizer Rates ◽  
Storage Temperatures

The present study evaluated the effect of NPK fertilizer (17:17:17) rates (0, 100, 200, 300 and 400 kg ha-1) on the postharvest quality of field and greenhouse grown pepino melons (Solanum muricatum Ait.) stored at room temperature (15-22°C) and at low temperature (7°C). The study was carried out in randomized complete block design with fruits from the field and greenhouse, five NPK fertilizer rates as treatments and the two storage temperatures replicated three times. Data were collected on percentage fruit weight loss (PWL), total soluble solids (TSS), firmness and shelf life. Results indicated that greenhouse and field grown fruits from the control and plants supplied with 100 kg NPK ha-1 had low PWL at both storage temperatures. Field grown fruits from the control stored at room temperature had the highest TSS and were firmer after 28 days of storage. Field grown fruits not supplied with fertilizer and stored at low temperature had a shelf life of 27 and 26 days in trial one and two respectively. Application of 100 kg NPK ha-1 and storage of pepino melon fruits at low temperature can be used to enhance quality and shelf life.

Photoluminescence Characterization of SiGe/Si Quantum-Well Wire Structures

1995 ◽  
Vol 379 ◽  
Author(s):  
S. Nilsson ◽  
H. P. Zeindl ◽  
A. Wolff ◽  
K. Pressel
Keyword(s):  
Quantum Well ◽  
Room Temperature ◽  
Molecular Beam ◽  
Optical Quality ◽  
Photoluminescence Spectra ◽  
Single Quantum Well ◽  
Quantum Well Wire ◽  
Carbon Interstitial

ABSTRACTLow-temperature photoluminescence measurements were performed in order to probe the optical quality of SiGe/Si quantum-well wire structures fabricated by electron-beam lithography and subsequent reactive ion etching, having the patterned polymethylmethacrylate resist as an etch mask. In addition, one set of quantum-well wire structures was post-treated by means of annealing in a hydrogen environment. Our results show that even for the smallest wires of about 100nm in width, the wires exhibit phonon-resolved photoluminescence spectra, similar to that from the molecular beam eptitaxially grown SiGe single quantum well which was used as starting material for the patterning process. After the patterning process a new sharp peak appears in the photoluminescence spectra at 0.97eV in photon energy. Our investigation suggests that this feature is introduced by damage during the patterning process and most probably identical to the G-line, which previously was identified as originating from the dicarbon centre (substitutional carbon-interstitial carbon) in Si. This centre is known to be a very common endproduct of irradiating Si near room temperature which is the case at our patterning process.

Physical Properties of Thin Films of GaAs and AlxGa1-xAs Grown by Solid-Arsenic-Based MOCVD

2014 ◽  
Vol 976 ◽  
pp. 25-29
Author(s):  
Roberto Castillo-Ojeda ◽  
Joel Diaz-Reyes ◽  
Miguel Galván-Arellano ◽  
Ramon Peña-Sierra
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Low Temperature ◽  
Growth Process ◽  
Carbon Incorporation ◽  
Infrared Measurements ◽  
Hall Effect Measurements ◽  
Low Temperature Photoluminescence

We have studied the optical properties of GaAs and AlxGa1-xAs thin films using low-temperature photoluminescence and Fourier transform infrared spectroscopy. The GaAs and its alloys were grown by MOCVD using solid arsenic instead of arsine, as the arsenic precursor. The gallium and aluminium precursors were trimethylgallium (TMGa) and trimethylaluminium (TMAl), respectively. Some difficulties for growing AlxGa1-xAs by solid-arsenic-based MOCVD system are the composition homogeneity of the layers and the oxygen and carbon incorporation during the growth process. The composition homogeneity of the films was evaluated by low-temperature photoluminescence. Infrared measurements on the samples allowed the identification of the residual impurities, which are carbon-substitutional, Ga2O3, molecular oxygen, humidity and two unidentified impurities. Samples grown at temperatures lower than 750°C were highly resistive, independently of the ratio V/III used; the samples grown at higher temperatures were n-type, as it was proved by Hall effect measurements.

scholarly journals Morphology and surface reconstructions of m-plane GaN

2002 ◽  
Vol 743 ◽  
Author(s):  
C. D. Lee ◽  
R. M. Feenstra ◽  
J. E. Northrup ◽  
L. Lymperakis ◽  
J. Neugebauer
Keyword(s):  
Molecular Beam Epitaxy ◽  
Low Temperature ◽  
Surface Morphology ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Structural Quality ◽  
Surface Reconstructions ◽  
Gan Buffer Layer

ABSTRACTM-plane GaN(1100) is grown by plasma assisted molecular beam epitaxy on ZnO(1100) substrates. A low-temperature GaN buffer layer is found to be necessary to obtain good structural quality of the films. Well oriented (1100) GaN films are obtained, with a slate like surface morphology. On the GaN(1100) surfaces, reconstructions with symmetry of c(2×2) and approximate “4×5” are found under N- and Ga-rich conditions, respectively. We propose a model for Ga-rich conditions with the “4×5” structure consisting of ≥ 2 monolayers of Ga terminating the GaN surface.

scholarly journals Improvement of Crystalline Quality of Group III Nitrides on Sapphire Using Low Temperature Interlayers

1999 ◽  
Vol 4 (S1) ◽  
pp. 870-877 ◽  
Author(s):  
H. Amano ◽  
M. Iwaya ◽  
N. Hayashi ◽  
T. Kashima ◽  
M. Katsuragawa ◽  
...  
Keyword(s):  
Low Temperature ◽  
Epitaxial Growth ◽  
Vapor Phase ◽  
Group Iii Nitrides ◽  
Crystalline Quality ◽  
Structural Quality ◽  
Group Iii

In organometallic vapor phase epitaxial growth of group III nitrides on sapphire, insertion of a low temperature interlayer is found to improve crystalline quality of AlxGa1−xN layer with x from 0 to 1. Here the effects of the low temperature deposited GaN or AlN interlayers on the structural quality of group III nitrides is discussed.

Tem Study of the Structure of Mbe GaAs Layers Grown at Low Temperature

1990 ◽  
Vol 198 ◽  
Author(s):  
Zuzanna Liliental-Weber
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Molecular Beam ◽  
Critical Thickness ◽  
Stacking Faults ◽  
Structural Quality ◽  
Crystalline Perfection ◽  
Transmission Electron ◽  
Low Temperature Gaas

ABSTRACTThe structural quality of GaAs layers grown at 200°C by molecular beam epitaxy (MBE) was investigated by transmission electron microscopy (TEM). We found that a high crystalline perfection can be achieved in the layers grown at this low temperature for thickness up to 3 μm. In some samples we observed pyramid-shaped defects with polycrystalline cores surrounded by microtwins, stacking faults and dislocations. The size of these cores increased as the growth temperature was decreased and as the layer thickness was increased. The upper surface of layers with pyramidal defects became polycrystalline at a critical thickness of the order of 3μm. We suggested that the low-temperature GaAs becomes polycrystalline at a critical thickness either because of a decrease in substrate temperature during growth or because strain induced by excess As incorporated in these layers leads to the formation of misoriented GaAs nuclei, thereby initiating polycrystalline growth. The pyramidal shape of the defects results from a growth-rate hierarchy of the low index planes in GaAs.

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