Unusual Properties of the Red and Green Luminescence Bands in Ga-rich GaN

2004 ◽  
Vol 831 ◽  
Author(s):  
M. A. Reshchikov ◽  
H. Morkoç
Keyword(s):  
Low Temperatures ◽  
Molecular Beam ◽  
Deep Level ◽  
Shallow Donor ◽  
Time Resolved ◽  
Temperature Range ◽  
Peak Intensity ◽  
Integrated Intensity ◽  
Valence Bands ◽  
Increasing Temperature

ABSTRACTWe studied photoluminescence (PL) from deep-level defects in GaN grown under Garich conditions at relatively low temperatures (700–800°C) by molecular-beam epitaxy (MBE). The dominant features of PL spectrum are red and green bands peaking respectively at ∼1.8 and ∼2.35 eV. Both PL bands decay exponentially at low temperatures (15 – 100 K) after pulsed excitation. The characteristic lifetime for the red band decreases by almost two orders of magnitude from 110 to 2 μs with increasing temperature from 15 to 100 K, while its integrated intensity after each pulse remains nearly unchanged in the same temperature range due to an increase in the peak intensity in the time-resolved PL curve. The lifetime of the green band remained unchanged in this temperature range. We suggest that these PL bands are caused by transitions between excited and ground states of some deep defects rather than transitions involving a shallow donor, conduction or valence bands.

Traps in Si-doped AlxGa1-xN Grown by Molecular Beam Epitaxy on Sapphire Characterized by Deep Level Transient Spectroscopy

2006 ◽  
Vol 955 ◽  
Author(s):  
Mo Ahoujja ◽  
S Elhamri ◽  
M Hogsed ◽  
Y. K. Yeo ◽  
R. L. Hengehold
Keyword(s):  
Molecular Beam Epitaxy ◽  
Deep Level Transient Spectroscopy ◽  
Molecular Beam ◽  
Deep Level ◽  
Unknown Origin ◽  
Shallow Donor ◽  
Related Point ◽  
Line Defects ◽  
Si Doped ◽  
Transient Spectroscopy

ABSTRACTDeep levels in Si doped AlxGa1−xN samples, with Al mole fraction in the range of x = 0 to 0.30, grown by radio-frequency plasma activated molecular beam epitaxy on sapphire substrates were characterized by deep level transient spectroscopy (DLTS). DLTS measurements show two significant electron traps, P1 and P2, in AlGaN at all aluminum mole fractions. The electron trap, P2, appears to be a superposition of traps A and B , both of which are observed in GaN grown by various growth techniques and are thought to be related to VGa-shallow donor complexes. Trap P1 is related to line defects and N-related point defects. Both of these traps are distributed throughout the bulk of the epitaxial layer. An additional trap P0 which was observed in Al0.20Ga0.80N and Al0.30Ga0.70N is of unknown origin, but like P1 and P2, it exhibits dislocation-related capture kinetics. The activation energy measured from the conduction band of the defects is found to increase with Al mole content, a behavior consistent with other III-V semiconductors.

Intrinsic N-Type Modulation Doping in Inp-Based Heterostructures

1996 ◽  
Vol 421 ◽  
Author(s):  
W.M. Chen ◽  
I.A. Buyanova ◽  
A. Buyanov ◽  
W.G. Bi ◽  
C.W. Tu
Keyword(s):  
Electron Transfer ◽  
Molecular Beam Epitaxy ◽  
Low Temperatures ◽  
Molecular Beam ◽  
Electron Gas ◽  
Shallow Donor ◽  
Modulation Doping ◽  
Gas Source ◽  
Shubnikov De Haas Oscillations ◽  
Lt Inp

AbstractWe propose and demonstrate a new doping approach, i.e. intrinsic doping, for n-type modulation doping in InP-based heterostructures. Instead of the conventional method of n-type doping by shallow donor impurities, grown-in intrinsic defects are utilized to provide the required doping without external doping sources. The success of this approach is clearly demonstrated by our results from InGaAs/InP heterostructures, where the required n-type doping in the InP barriers is provided by Pin antisites, preferably introduced during off-stoichiometric growth of InP at low temperatures (LT-InP) by gas source molecular beam epitaxy. A twodimensional electron gas (2DEG) is shown to be formed near the InGaAs/InP heterointerface as a result of electron transfer from the LT-InP to the InGaAs active layer, from studies of Shubnikov-de Haas oscillations and photoluminescence. The concentration of the 2DEG is determined to be as high as 1.15×1012 cm−2, where two subbands of the 2DEG are readily occupied.

scholarly journals Vacuum-Ultraviolet Absorption Spectra of Icy C2H4 at 13–60 K

2021 ◽  
Vol 8 ◽  
Author(s):  
Jen-Iu Lo ◽  
Rana Ghosh ◽  
Hsiao-Chi Lu ◽  
Wei-Hsiu Hung ◽  
Bing-Ming Cheng
Keyword(s):  
Absorption Spectra ◽  
Light Source ◽  
Wavelength Range ◽  
Low Temperatures ◽  
Vacuum Ultraviolet ◽  
Detailed Examination ◽  
Isosbestic Point ◽  
Thermal Variation ◽  
Temperature Range ◽  
Increasing Temperature

The thermal variation of absorption spectra of icy ethene in wavelength range 105–220 nm was measured from 13 to 100 K using a synchrotron as light source. Sublimation of icy ethene began above 62 K, resulting in decreasing absorption. The absorption of icy ethene increased at wavelengths less than about 150 nm with increasing temperature from 13 to 60 K, but decreased beyond above 150 nm. According to detailed examination, the absorption spectra of icy ethene intersected at isosbestic point 147.0 nm from 13 to 17 K, whereas those varied absorption profiles crossed at another point, 150.6 nm, from 23 to 60 K. These results indicate that ethene ices might exhibit three structures within temperature range 13–60 K. This work enhances our understanding of the spectra of icy ethene at low temperatures and our knowledge of its astrochemistry and astrophysics in cold astro-environments.

HYDROGEN IN CRYSTALLINE SEMICONDUCTORS: PART I—SILICON

1994 ◽  
Vol 08 (09) ◽  
pp. 1093-1158 ◽  
Author(s):  
S.J. PEARTON
Keyword(s):  
Vapor Deposition ◽  
Low Temperatures ◽  
Molecular Beam ◽  
Hydrogen Diffusion ◽  
Deep Level ◽  
Chemical Vapor ◽  
Device Fabrication ◽  
Device Operation ◽  
Diffusion Profiles

Hydrogen plays an important role in the properties of Si because of its ability to passivate the electrical activity of shallow dopants and deep level impurities. This passivation can occur during virtually every stage of crystal growth, device fabrication or device operation due to the rapid diffusivity of hydrogen at low temperatures and the fact that it is a component of virtually every gas or liquid that comes in contact with Si. We review the ability of hydrogen to form neutral complexes with dopants and impurities, give examples of hydrogen diffusion profiles in doped and undoped Si, and mention the role of hydrogen during chemical vapor deposition and molecular beam epitaxy of Si.

Effect of Growth Temperature on Thin Films Structure and Blue Photoluminescence Spectrum of Nanocrystalline ZnO Films

2013 ◽  
Vol 385-386 ◽  
pp. 23-26
Author(s):  
Guo Li Song ◽  
Hong Liang
Keyword(s):  
Thin Films ◽  
Growth Temperature ◽  
Film Growth ◽  
Blue Emission ◽  
Shallow Donor ◽  
Zno Films ◽  
Peak Intensity ◽  
Integrated Intensity ◽  
Strong Blue Emission ◽  
Quartz Substrates

Nanocrystalline ZnO films were deposited on Quartz substrates by RFMS. A strong blue emission (430 ~ 460nm) and UV emission were observed. PL of the integrated intensity and peak intensity, XRD peak intensity and half width (FWHM) and their relationship with growth temperature are given. It was found that 300 °C ~ 350 °C temperature is favorable to the growth of thin film growth, and can get a strong blue emission spectrum. It was initially confirmed that the blue emission (430 ~ 460nm) of ZnO thin films is from the shallow donor electrons to the valence band on the top of the transition which is formed by the Vo or Zni, or Vo to the formation of shallow donor level of Vzn the formation of shallow acceptor level of the composite.

scholarly journals Effect of hydrogen on the electrical resistance of NbSe2 in a wide temperature range

2021 ◽  
Author(s):  
A. Chroneos ◽  
G. Ya. Khadzhai ◽  
V. I. Biletskyi ◽  
M. V. Kislitsa ◽  
R. V. Vovk
Keyword(s):  
Solid Solution ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
Charge Density Wave ◽  
Density Wave ◽  
Temperature Range ◽  
Niobium Diselenide ◽  
Dissolved Hydrogen ◽  
A Charge ◽  
Increasing Temperature

AbstractThe electrical resistivity of niobium diselenide (NbSe2) with hydrogen was investigated in the temperature range Tc – 300 K. It was determined that hydrogen inhibits the formation of a charge density wave. It was shown that hydride phase with niobium is formed due to hydrogen in NbSe2 layers at low temperatures, which decomposes with increasing temperature to form a solid solution. The temperature dependence of the resistivity is approximated by the Bloch–Grüneisen function. The approximation parameters vary depending on the amount of dissolved hydrogen.

DX CENTERS IN AlGaN

1999 ◽  
Vol 13 (11) ◽  
pp. 1363-1378 ◽  
Author(s):  
M. D. McCLUSKEY ◽  
C. G. VAN de WALLE ◽  
N. M. JOHNSON ◽  
D. P. BOUR ◽  
M. KNEISSL
Keyword(s):  
Deep Level ◽  
Far Infrared ◽  
Shallow Donor ◽  
Experimental Investigations ◽  
Nitride Semiconductors ◽  
Dx Centers ◽  
Free Carriers ◽  
Peak Intensity ◽  
Oxygen Impurities ◽  
Raman Peak Intensity

In this letter, recent theoretical and experimental investigations of DX centers in Al x Ga 1-x N are reviewed. Due to the technological importance of III–V nitride semiconductors, studies of deep-level defects in AlGaN have attracted a great deal of interest. Oxygen impurities form DX centers in GaN under hydrostatic pressure and in Al x Ga 1-x N alloys. For GaN under pressures greater than 20 GPa, the DX level emerges from the conduction band, leading to a decrease in the free-electron concentration. The localization of free carriers leads to a decrease in the far-infrared absorption and an increase in the LO Raman peak intensity. In Al x Ga 1-x N alloys, Hall effect and persistent photoconductivity measurements indicate that the DX state is energetically favorable for x>0.3. The experimental data for oxygen DX centers are in excellent agreement with first-principles calculations. Experiments have shown that silicon remains a shallow donor up to at least x=0.5 and theory indicates that it may remain shallow up to x=1.

Growth Temperature Effects on Deep-Levels in Si Grown by Low Temperature Molecular Beam Epitaxy

2002 ◽  
Vol 745 ◽  
Author(s):  
Sung-Yong Chung ◽  
Paul R. Berger ◽  
Z-Q. Fang ◽  
Phillip E. Thompson
Keyword(s):  
Growth Temperature ◽  
Deep Level Transient Spectroscopy ◽  
Molecular Beam ◽  
Deep Level ◽  
Trap Density ◽  
Electron Traps ◽  
Temperature Electron ◽  
Transient Spectroscopy ◽  
Increasing Temperature ◽  
And Diffusion

ABSTRACTDeep-level transient spectroscopy (DLTS) measurements were performed on Si:Sb and Si:B n+-p step junction diodes grown by LT-MBE at various growth temperatures. The trap density dependence on growth temperature decreases with increasing temperature. However, segregation and diffusion increase with increasing temperature. Electron traps, E1 (0.42–0.45eV) and E2 (0.257eV), and hole traps, H1 (0.38–0.41eV), were found in B-doped layer grown at 370°C, 420°C, 500°C, and 600°C. These traps have been characterized by their capture cross-section, activation energy level, and trap density. The origins of the dominating electron traps are hypothesized as the association with pure divacancy defects. E1 level can be assigned for singly negatively charged divacancy V(0/-) + α and E2 level for doubly negatively charged divacancy V(-2/-).

scholarly journals Investigation of Micromorphology and Carrier Recombination Dynamics for InGaN/GaN Multi-Quantum Dots Grown by Molecular Beam Epitaxy

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1312
Author(s):  
Xue Zhang ◽  
Wenxian Yang ◽  
Zhiwei Xing ◽  
Haibing Qiu ◽  
Ying Gu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Light Emitting Diode ◽  
Temperature Stability ◽  
Nonradiative Recombination ◽  
Uniform Size ◽  
Time Resolved ◽  
Decay Times ◽  
Increasing Temperature

InGaN quantum dots (QDs) are promising candidates for GaN-based all-visible optoelectronic devices such as micro light-emitting diode and laser. In this study, self-assembled InGaN/GaN multi-quantum dots (MQDs) have been grown by plasma-assisted molecular beam epitaxy on c-plane GaN-on-sapphire template. A high density of over 3.8 × 1010 cm−2 is achieved and InGaN QDs exhibit a relatively uniform size distribution and good dispersity. Strong localization effect in as-grown InGaN QDs has been evidenced by temperature-dependent photoluminescence (PL). The variation of peak energy is as small as 35 meV with increasing temperature from 10 K to 300 K, implying excellent temperature stability of emission wavelength for InGaN MQDs. Moreover, the radiative and nonradiative recombination times were calculated by time-resolved PL (TRPL) measurements, and the temperature dependence of PL decay times reveal that radiative recombination dominates the recombination process due to the low dislocation density of QDs structure.

Features of radiothermoluminescence of polypropylene and ethylene propylenediene elastomer SKEPT-4044 compositions with nanoscale metal-containing fillers

2020 ◽  
pp. 66-73
Author(s):  
A.M. Magerramov ◽  
◽  
N.I. Kurbanova ◽  
M.N. Bayramov ◽  
N.A. Alimirzoyeva ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Molecular Mobility ◽  
Fe3o4 Nanoparticles ◽  
Low Temperatures ◽  
Frost Resistance ◽  
Relaxation Processes ◽  
Ethylene Propylene ◽  
Temperature Range ◽  
Β Relaxation

Using radiothermoluminescence (RTL), the molecular mobility features in the temperature range of 77-300 K were studied for the polypropylene (PP)/ethylene propylene diene elastomer SKEPT-4044 with NiO, Cu2O and Fe3O4 nanoparticles (NPs) based on ABS-acrylonitrile butadiene or SCS-divinyl styrene matrices. It has been shown that the introduction of nanofillers in PP significantly affects the nature and temperature of γ- and β-relaxation processes, while the region of manifestation of the β-process noticeably shifts to the region of low temperatures. Composites with Cu2O NPs have a higher β-transition temperature Tβ than composites with other NPs. It was found that PP/SKEPT-4044 composites with Cu2O NPs with a dispersion of 11-15 nm and acrylonitrile butadiene thermoplastics have optimal frost resistance compared to other compositions.

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