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Articles 1 - 21 of 21
Full-Text Articles in Physics
Photoluminescence Of Beryllium-Related Defects In Gallium Nitride, Mykhailo Vorobiov, Mykhailo Vorobiov
Photoluminescence Of Beryllium-Related Defects In Gallium Nitride, Mykhailo Vorobiov, Mykhailo Vorobiov
Theses and Dissertations
This study explores the potential of beryllium (Be) as an alternative dopant to magnesium (Mg) for achieving higher hole concentrations in gallium nitride (GaN). Despite Mg prominence as an acceptor in optoelectronic and high-power devices, its deep acceptor level at 0.22 eV above the valence band limits its effectiveness. By examining Be, this research aims to pave the way to overcoming these limitations and extend the findings to aluminum nitride and aluminum gallium nitride (AlGaN) alloy. Key contributions of this work include. i)Identification of three Be-related luminescence bands in GaN through photoluminescence spectroscopy, improving the understanding needed for further material …
Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov
Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov
Theses and Dissertations
This thesis devoted to the experimental studies of yellow and blue luminescence (YL and BL relatively) bands in Gallium Nitride samples doped with C and Si. The band BLC was at first observed in the steady-state photoluminescence spectrum under high excitation intensities and discerned from BL1 and BL2 bands appearing in the same region of the spectrum. Using the time-resolved photoluminescence spectrum, we were able to determine the shape of the BLC and its position at 2.87 eV. Internal quantum efficiency of the YL band was estimated to be 90\%. The hole capture coefficient of the BLC …
Thermal Quenching Of Photoluminescence In Zno And Gan, Nahla Albarakati
Thermal Quenching Of Photoluminescence In Zno And Gan, Nahla Albarakati
Theses and Dissertations
Investigation of the thermal quenching of photoluminescence (PL) in semiconductors provides valuable information on identity and characteristics of point defects in these materials, which helps to better understand and improve the properties of semiconductor materials and devices. Abrupt and tunable thermal quenching (ATQ) of PL is a relatively new phenomenon with an unusual behavior of PL. This mechanism was able to explain what a traditional model failed to explain. Usually, in traditional model used to explain “normal” quenching, the slope of PL quenching in the Arrhenius plot determines the ionization energy of the defect causing the PL band. However, in …
Study Of The Photoluminescence Spectra Of Mg-Doped Gan, Puranjan Ghimire
Study Of The Photoluminescence Spectra Of Mg-Doped Gan, Puranjan Ghimire
Theses and Dissertations
We have studied luminescence properties of Mg-doped GaN grown by hydride vapor phase epitaxy. Steady state photoluminescence (PL) spectra have been analyzed. Exciton, ultraviolet luminescence (UVL) and blue luminescence (BL) bands are the dominant PL bands in the spectra. At low temperature, Exciton and UVL bands show almost no shift with excitation intensity, whereas the BL band blueshifts by almost 0.4 ���� with increasing excitation intensity by seven orders of magnitude. Such shifting nature of bands with excitation intensity is explained by assuming that the BL band is detected from the region of the sample where potential fluctuations are very …
Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian
Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian
Theses and Dissertations
Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …
Time-Resolved Photoluminescence Studies Of Point Defects In Gan, Joy Dorene Mcnamara
Time-Resolved Photoluminescence Studies Of Point Defects In Gan, Joy Dorene Mcnamara
Theses and Dissertations
Time-resolved photoluminescence (TRPL) measurements paired with steady-state photoluminescence (SSPL) measurements can help to determine the PL lifetime, shape and position of unresolved bands, capture coefficients, and concentrations of free electrons and defects.PL bands that are obscured in the SSPL spectra can be accurately revealed by TRPL measurements. TRPL measurements are able to show if the PL band originates from an internal transition between different states of the same defect. The main defect-related PL bands in high-purity GaN grown by hydride vapor phase epitaxy (HVPE) which have been investigated are the ultraviolet, blue, green, yellow and red luminescence bands (UVL, BL, …
The Effect Of Temperature On The Electrical And Optical Properties Of P-Type Gan, Joy Mcnamara
The Effect Of Temperature On The Electrical And Optical Properties Of P-Type Gan, Joy Mcnamara
Theses and Dissertations
The development of gallium nitride (GaN) light emitting devices has reached extraordinary echelons. As such, the characterization and analysis of the behavior of GaN materials is essential to the advancement of GaN technology. In this thesis, the effect of temperature on the optical and electrical properties of p-type GaN is investigated. The GaN samples used in this work were grown by various methods and studied by Kelvin probe and photoluminescence (PL) techniques. Specifically, the surface photovoltage (SPV) behavior and PL data were analyzed at different temperatures and illumination intensities. Using the SPV results, we show that p-type GaN exhibits n-type …
Thermal Quenching Of Photoluminescence From Gan, Anita Olsen
Thermal Quenching Of Photoluminescence From Gan, Anita Olsen
Theses and Dissertations
GaN is a III-V semiconductor that is a promising material used in production of light emitting devices and high power/high frequency electronics. The electronic and optical properties of GaN are subdued by defects that occur during the growth processes of this material. The emitted photoluminescence (PL) from optically excited GaN gives insight into the origins and effects of point defects within the crystal lattice structure of GaN. In this study, PL spectroscopy is used to examine and analyze the point defects that occur in Zn-doped GaN. The blue luminescence band seen in undoped and Zn-doped GaN have identical fine structure …
Electrical And Optical Characterization Of Si-Ge-Sn, Merle D. Hamilton
Electrical And Optical Characterization Of Si-Ge-Sn, Merle D. Hamilton
Theses and Dissertations
The electrical characterization of boron-doped p-Si0.08Ge0.90Sn0.02/p-Ge(100) and p-Si0.112Ge0.86Sn0.028/n-Si(100) with various epilayer thicknesses was measured using the Hall effect. The room temperature sheet carrier concentration ranged from 1.21 x 1013 – 1.32 x 1016 cm-2. The room temperature mobilities were measured to be between 166 and 717 cm2/V·s, depending on sample composition. In the low temperature regime, the mobility was mainly affected by ionized impurity scattering. In the high temperature regime, the mobility was mainly affected by …
Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers, Bradley S. Jones
Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers, Bradley S. Jones
Theses and Dissertations
The properties of thin, cerium activated, yttrium aluminum garnet (YAG:Ce), scintillating fiber-shaped crystals were investigated for particle tracking and calorimetric applications such as Compton imaging of Special Nuclear Material from remote platforms at standoff ranges. Silicon photomultipliers (SiPMs) are relatively new, efficient, single photon sensitive, solid-state photodiode arrays which are well suited for the readout of scintillating fibers. Using SiPMs, the scintillation decay time profiles of six 400 micrometers YAG:Ce fiber crystals were measured under alpha and gamma irradiation. Interestingly, the observed decay times in the thin fibers were substantially slower than values for bulk single crystal YAG:Ce reported in …
Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis
Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis
Theses and Dissertations
Mid-Wave Infrared (MWIR) semiconductors are of use to the Air Force for several applications. Ultrafast spectroscopy can be used to better quantify the effectiveness of semiconductor opto-electronic devices. The objective of this thesis was to improve the procedure for taking ultrafast, time-resolved measurements of photoluminescence from MWIR semiconductors. Previous work has used a mode-locked titanium sapphire (Ti:Saph) laser to excite the semiconductor sample and to upconvert the photoluminescence from the semiconductor. Work completed in this thesis improved on the techniques developed during previous work. A synchronous Optical Parameter Oscillator (OPO) will be used to convert the Ti:Saph laser (0.830 µm) …
Limitations In Time Resolved Photoluminescence Of Gallium Nitride Using A Streak Camera, Thomas R. Jost
Limitations In Time Resolved Photoluminescence Of Gallium Nitride Using A Streak Camera, Thomas R. Jost
Theses and Dissertations
Semiconductor performance is often characterized in terms of the rate at which its carrier recombination processes occur. Carrier recombination, including radiative, and Shockley-Read-Hall and Auger (both nonradiative), occurs at ultra-fast times in the picosecond or femtosecond regimes. A device which can measure both spectral data and temporal phenomena at this speed is the streak camera. The capability to do time-resolved spectroscopy of wide band gap semiconductors using a streak camera has been established at AFIT for the first time. Time resolved photoluminescence (TRPL) from samples of gallium nitride were measured at temperatures of 5 K over spectral bands of 36.6 …
Optical Characterization And Modeling Of Compositionally Matched Indium Arsenide-Antimonide Bulk And Multiple Quantum Well Semiconductors, Scott C. Phillips
Optical Characterization And Modeling Of Compositionally Matched Indium Arsenide-Antimonide Bulk And Multiple Quantum Well Semiconductors, Scott C. Phillips
Theses and Dissertations
Indium arsenide-antimonide (InAsSb) semiconductors have been determined to emit in the 3-5 micrometer range, the window of interest for countermeasures against infrared electro-optical threats. This experiment set out to cross the bulk to quantum well characterization barrier by optically characterizing two sets of compositionally matched type I quantum well and bulk well material samples. Absorption measurements determined the band gap energy of the bulk samples and the first allowed subband transition for the quantum wells. By collecting absorption spectra at different temperatures, the trend of the energy transitions was described by fitting a Varshni equation to them. The expected result …
Building Blocks For Time-Resolved Laser Emission In Mid-Infrared Quantum Well Lasers, Gabriel D. Mounce
Building Blocks For Time-Resolved Laser Emission In Mid-Infrared Quantum Well Lasers, Gabriel D. Mounce
Theses and Dissertations
The objective of this research is to improve the performance of mid-infrared semiconductor quantum-well lasers. Lasers operating in the mid-infrared are useful for many Air Force applications which include infrared (IR) countermeasures in particular. Countermeasure applications require lasers that are compact, and able to emit at high powers while operating at room temperature. Limits to power increases are seen in the transverse modal development of laser oscillation. These modes typically form in the waveguiding active region contributing to the laser output. However, competing modes outside of this region also develop when the confining structural layers have the right characteristics. These …
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Theses and Dissertations
In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Photoluminescence Of Single Quantum Well Structures In Gallium Arsenide, Christian A. Bartholomew
Theses and Dissertations
The continued development of state-of the-art semiconductor technologies and devices by the United States Air Force and the Department of Defense requires accurate and efficient techniques to evaluate and model these new materials. Of particular interest to the Air Force are quantum well structures which can be used for small-scale laser sources in fly-by-light applications, as efficient infrared countermeasures to heat-seeking missiles, or as advanced seekers in optically guided missiles. This thesis provides the initial experimental procedures and data necessary to begin producing accurate yet robust models. Although carrier effective masses could not be evaluated using hot-electron photoluminescence, photoluminescence excitation …
Photoluminescence Study Of Gan Implanted With Erbium And Erbium-Oxygen, Lori R. Everitt
Photoluminescence Study Of Gan Implanted With Erbium And Erbium-Oxygen, Lori R. Everitt
Theses and Dissertations
Erbium emits at 1540 nm, which propagates well through fiber optic cables. This work studies the photoluminescence (PL) from GaN, GaN implanted with Er alone, and GaN implanted with both Er and O as functions of excitation laser energy and sample temperature. When the exciton bound to a neutral donor recombined, a photon was emitted at 3.47 eV. A photon emitted at 3.457 eV may have been evidence of the recombination of an exciton bound to a neutral acceptor. Second, the Er-ion transitions were observed in two groups around 0.805 and 1.25 eV. The PL intensity was measured at four …
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Theses and Dissertations
Recombination mechanisms in mid-IR semiconductor lasers are strongly dependent on the carrier density of the active region. The objective of this research is to improve previous carrier density estimates through the incorporation of spectral information. One hundred photoluminescence (PL) spectra were calculated for a variety of carrier densities. Calculations were made for an InAsSb/InAlAsSb multiple quantum well laser sample assuming parabolic bands. The widths of the calculated spectral profiles were tabulated as a function of carrier density. Actual spectra were measured using the Ultrafast Mid-Infrared Photoluminescence System, which uses upconversion to measure the PL intensity in time steps smaller than …
Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter
Photoluminescence And Electroluminescence Of Erbium And Neodymium Implanted Semiconductors, James R. Hunter
Theses and Dissertations
Low temperature photoluminescence (PL) and electroluminescence (EL) measurements were used to study the excitation of erbium- and neodymium-implanted GaAs and AlxGa1-xAs (x=0. 1, 0.3) pn-junctions. The rare-earth (RE) emissions were investigated as a function of ion dose, aluminum mole fraction, laser excitation power, and applied forward bias voltage for the implanted samples. Low temperature PL was also measured from Er doped silicon grown by the metalorganic chemical vapor-phase deposition (MOCVD) method using various growth parameters.. The MOCVD-grown Si samples were studied as a function of metalorganic source temperature, silane (SiH4) flow, growth time, and …
The Optical Emission And Absorption Properties Of Silicon-Germanium Superlattice Structures Grown On Non-Conventional Silicon Substrate Orientation, Theodore L. Kreifels
The Optical Emission And Absorption Properties Of Silicon-Germanium Superlattice Structures Grown On Non-Conventional Silicon Substrate Orientation, Theodore L. Kreifels
Theses and Dissertations
Optical emission and absorption properties of Si1-x Gex/Si superlattices grown on (100), (110), and (111) Si substrates were investigated to determine the optimal growth conditions for these structures to be used as infrared detectors. Fully-strained Si1-x Gex/Si superlattices were grown by molecular beam epitaxy MBE and examined using low-temperature photoluminescence PL to identify no-phonon and phonon-replica interband transitions across the alloy bandgap. Phonon-resolved emission was most intense for undoped quantum wells grown at 710°C for all three silicon orientations. Room temperature absorption measurements were conducted on (100) and (110) Si1-x Gex/Si …
The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee
The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee
Theses and Dissertations
This study on praseodymium Pr luminescence in AlxGa1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 1012 to 5 x 1013 sq cm into AlxGa1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …