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Characterizing Composition Modulations in InAs/AIAs Short-Period Superlattices

Description: The formation of quantum wires has much interest due to their novel electronic properties which may lead to enhanced optoelectronic device performance and greater photovoltaic efficiencies. One method of forming these structures is through spontaneous lateral modulation found during the epitaxial growth of III/V alloys. In this paper, we report and summarize our investigations on the formation of lateral moduation in the MBE grown InAlAs/InP(001) system. This system was grown as a short-period … more
Date: April 26, 1999
Creator: Ahrenkiel, S. P.; Follstaedt, D. M.; Jones, E. D.; Lee, S. R.; Mascarenhas, A.; Mirecki-Millunchick, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs

Description: A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with … more
Date: November 23, 1998
Creator: Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B. et al.
Partner: UNT Libraries Government Documents Department
open access

Photoluminescence Studies of Lateral Composition Modulated Short-Period AlAs/InAs Superlattices

Description: We present low temperature photoluminescence data for a series of spontaneous lateral composition modulation in (AlAs){sub m}/(InAs){sub n} short period superlattices on InP with differing average lattice constants, i.e., varying global strain. The low temperature photoluminescence peak energies were found to be much lower than the corresponding energy expected for the equivalent In{sub x}Al{sub 1{minus}x}As alloy. The bandgap energy reductions are found to approach 500 meV and this reduction i… more
Date: January 4, 1999
Creator: Ahrenkiel, S. P.; Follstaedt, D. M.; Jones, E. D.; Lee, S. R.; Mascarenhas, A.; Mirecki-Millunchick, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Spectroscopic properties of colloidal indium phosphide quantum wires

Description: Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence ef… more
Date: July 11, 2008
Creator: Wang, Lin-Wang; Wang, Fudong; Yu, Heng; Li, Jingbo; Hang, Qingling; Zemlyanov, Dmitry et al.
Partner: UNT Libraries Government Documents Department
open access

Spectral utilization in thermophotovoltaic devices

Description: Multilayer assemblies of epitaxially-grown, III-V semiconductor materials are being investigated for use in thermophotovoltaic (TPV) energy conversion applications. It has been observed that thick, highly-doped semiconductor layers within cell architectures dominate the parasitic free-carrier absorption (FCA) of devices at wavelengths above the bandgap of the semiconductor material. In this work, the wavelength-dependent, free-carrier absorption of p- and n-type InGaAs layers grown epitaxially … more
Date: 1997~
Creator: Clevenger, Marvin B. & Murray, Christopher S.
Partner: UNT Libraries Government Documents Department
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Spontaneous lateral composition modulation in InAlAs and InGaAs short-period superlattices

Description: The microstructure of spontaneous lateral composition modulation along the [110] direction has been studied in (InAs){sub n}/(AlAs){sub m} short-period superlattices grown by molecular beam epitaxy on (001) InP. X-ray diffraction and transmission electron microscopy show that global strain ({var_epsilon}) in the superlattice reduces the degree of composition modulation, which disappears for the absolute value of {var_epsilon} > 0.7%. For tensile strains of {var_epsilon} {approx} +0.4%, they fin… more
Date: July 11, 1997
Creator: Follstaedt, D. M.; Twesten, R. D.; Millunchick, J. M.; Lee, S. R.; Jones, E. D.; Ahrenkiel, S. P. et al.
Partner: UNT Libraries Government Documents Department
open access

Spectroscopic study of partially-ordered semiconductor heterojunction under high pressure and high magnetic field

Description: Photoluminescence upconversion (PLU) is a phenomenon in which a sample emits photons with energy higher than that of the excitation photon. This effect has been observed in many materials including rare earth ions doped in insulating hosts and semiconductor heterostructures without using high power lasers as the excitation source. Recently, this effect has been observed also in partially CuPt-ordered GaInP{sub 2} epilayers grown on GaAs substrates. As a spectroscopic technique photoluminescence… more
Date: December 31, 2000
Creator: Yu, P.Y.; Martinez, G.; Zeman, J. & Uchida, K.
Partner: UNT Libraries Government Documents Department
open access

High-performance, lattice-mismatched InGaAs/InP monolithic interconnected modules (MIMs)

Description: High performance, lattice-mismatched p/n InGaAs/lnP monolithic interconnected module (MIM) structures were developed for thermophotovoltaic (TPV) applications. A MIM device consists of several individual InGaAs photovoltaic (PV) cells series-connected on a single semi-insulating (S.I.) InP substrate. Both interdigitated and conventional (i.e., non-interdigitated) MIMs were fabricated. The energy bandgap (Eg) for these devices was 0.60 eV. A compositionally step-graded InPAs buffer was used to a… more
Date: October 1, 1998
Creator: Fatemi, Navid S.; Wilt, David M.; Hoffman, Richard W., Jr.; Stan, Mark S.; Weizer, Victor G.; Jenkins, Phillip P. et al.
Partner: UNT Libraries Government Documents Department
open access

High-Efficiency, Low-Voltage, Compound Semiconductor Devices for Microwave and MM-Wave Power Amplifiers

Description: Improvements in the last decade in InP materials growth, device processing techniques, characterization, and circuit design have enabled solid-state power performance through 122 GHz. Although originally targeted for low-noise and power performance at mm-wave frequencies (>30 GHz), InP HEMTs could become the preferred device for frequencies as low as 800 MHz. This investment has benefited the microwave frequency regime with higher efficiency and power densities at lower operating voltages. S… more
Date: July 14, 1999
Creator: Chao, P.C.; Hietala, V.M.; Kong, W. & Sloan, Lynn R.
Partner: UNT Libraries Government Documents Department
open access

Effect of exciton localization and delocalization on magnetic-field-dependent photoluminescence linewidths in semiconductors

Description: Theory and data are presented for the photoluminescence linewidth in ordered and disordered semiconductor alloys (In{sub 0.48}Ga{sub 0.52}P) at low temperatures. In disordered (ordered) systems, the linewidth is due to exciton localization (exciton-impurity scattering) and increases (decreases) as a function of the field in agreement with the data.
Date: August 1, 1993
Creator: Lyo, S. K.; Jones, E. D. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department
open access

Detection of lateral composition modulation by magnetoexciton spectroscopy

Description: An experimental signature for detecting spontaneous lateral composition modulation in a (InAs){sub n}/(GaAs){sub m} short period superlattice on an InP substrate based on magnetoexciton spectroscopy described. The authors find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulation. more
Date: July 10, 1997
Creator: Jones, E. D.; Millunchick, J. M.; Follstaedt, D.; Lee, S.; Reno, J.; Twesten, R. D. et al.
Partner: UNT Libraries Government Documents Department
open access

Upconversion of near GaAs bandgap photons to GaInP{sub 2} emission at the GaAs/(ordered) GaInP{sub 2} heterojunction

Description: The authors have observed upconversion of photoluminescence in several partially ordered GaInP{sub 2} epilayers grown on [100] oriented GaAs substrates. They found that this upconversion occurs even when the excitation photon energy is below the bandgap of GaAs but near the electron-acceptor transitions at {approximately} 1.49 eV. A two-step two-photon absorption model in which the conduction band alignment at the GaAs/GaInP{sub 2} is of type 2 is proposed to explain the results.
Date: September 1, 1996
Creator: Teo, K. L.; Su, Z. P.; Yu, P. Y. & Uchida, K.
Partner: UNT Libraries Government Documents Department
open access

The Growth of InAsSb/InAsP Strained-Layer Superlattices for Use in Infrared Emitters

Description: We describe the metal-organic chemical vapor deposition growth of InAsSb/InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. These SLSs were grown at 500{degrees}C, and 200 torr in a horizontal quartz reactor using TMIn, TESb, AsH{sub 3},and PH{sub 3}. By changing the layer thickness and composition we have prepared structures with low temperature ({le}20K) photoluminescence wavelengths ranging from 3.2 to 4.4 {mu}m. Excellent performance was observed for an… more
Date: June 1, 1997
Creator: Biefeld, R. M.; Allerman, A. A. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department
open access

Microstructure of compositionally modulated InAlAs

Description: The authors have observed spontaneous, lateral composition modulation in tensile InAlAs alloy films grown as short-period superlattices on InP (001). They have analyzed these films using transmission electron microscopy, x-ray reciprocal space mapping, and polarized photoluminescence spectroscopy. They find the growth front is nonplanar, exhibiting {approximately} 2 nm deep cusps aligned with the In-rich regions of the compositionally modulated films. In addition to the measured 15 nm wavelengt… more
Date: December 31, 1996
Creator: Twesten, R. D.; Millunchick, J. M.; Lee, S. R.; Follstaedt, D. M.; Jones, E. D.; Ahrenkiel, S. P. et al.
Partner: UNT Libraries Government Documents Department
open access

CuPt-type ordering of MOCVD In{sub 0.49}Al{sub 0.51}P.

Description: CuPt-type ordering in In{sub 0.49}Al{sub 0.51}P is studied by TEM. The lattice-matched film was grown by MOCVD on a GaAs substrate oriented 10{sup o} off (001) towards [110], at 650 C and 25 nm/min. TEM [110] and [1{bar 1}0] cross-sections (XS) were made by wedge polishing and 2 kV Ar ion milling. In CuPt-type ordering of In{sub 0.52}Ga{sub 0.48}P, alternating In-Ga-In-Ga {l_brace}111{r_brace} planes of group III atoms produce 1/2 {bar 1}11 and 1/2 1{bar 1}1 order spots in the 110 SADP, while t… more
Date: March 14, 2002
Creator: Kosel, T. H.; Hall, D. C.; Dupuis, R. D.; Heller, R. D. & Cook, R. E.
Partner: UNT Libraries Government Documents Department
open access

Magnetic field dependence of up-converted photoluminescence in partially ordered GaInP{sub 2}/GaAs up to 23 T

Description: The influence of a strong magnetic field on the up-converted photoluminescence (PL) spectra of partially ordered layers of GaInP{sub 2} grown on GaAs substrate have been investigated. The up-converted PL spectra exhibit 2 peaks. The position of the low energy peak is close to that of the peak observed in Pl spectra excited by above GaInP{sub 2} bandgap light while the other peak occurs at about 30 meV higher in energy. Both peaks show a linear dependence on B between 0 and 23 T suggesting that … more
Date: September 1, 1996
Creator: Zeman, J.; Martinez, G.; Yu, P.Y. & Uchida, K.
Partner: UNT Libraries Government Documents Department
open access

Comparison of experimental and theoretical gain-current relations in GaInP quantum well lasers

Description: The authors compare the results of a microscopic laser theory with gain and recombination currents obtained from experimental spontaneous emission spectra. The calculated absorption spectrum is first matched to that measured on a laser, ensuring that the quasi-Fermi levels for the calculation and the experiment (spontaneous emission and gain) are directly related. This allows one to determine the inhomogeneous broadening in their experimental samples. The only other inputs to the theory are lit… more
Date: January 10, 2000
Creator: Smowton, P. M.; Chow, W. W. & Blood, P.
Partner: UNT Libraries Government Documents Department
open access

Effect of High-Voltage Heterojunction Bipolar Transistor Collector Design on f(T) and f(MAX)

Description: High-speed InGaP/GaAs heterojunction bipolar transistors (HBTs) for high-voltage circuit applications have been investigated. In order to obtain ideal IV characteristics, a lightly doped (N{sub DC} = 7.5 x 10{sup 15} cm{sup {minus}3}) thick (W{sub C} = 3.5 {micro}m) layer of GaAs was used as the collector layer. The devices fabricated have shown breakdown voltage exceeding 65 V. Device operated at up to a 60V bias, which is the highest operating voltage reported up to date for single heterojunc… more
Date: March 2, 1999
Creator: Ashby, C. I. H.; Baca, A. G.; Chang, P. C. & Hietala, V. M.
Partner: UNT Libraries Government Documents Department
open access

Detection of lateral composition modulation in a (InAs){sub n}/(GaAs){sub n} short period superlattice on InP by magnetoexciton spectroscopy

Description: An experimental signature for detecting spontaneous lateral composition modulation in a (InAs){sub n}/(GaAs){sub n} short period superlattice on a InP substrate based on magnetoexciton spectroscopy is presented. The authors find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulati… more
Date: March 1, 1997
Creator: Jones, E. D.; Mirecki-Millunchick, J.; Follstaedt, D.; Hafich, M.; Lee, S.; Reno, J. et al.
Partner: UNT Libraries Government Documents Department
open access

Effect of surface steps on the microstructure of lateral composition modulation

Description: Growth of InAs/AlAs short-period superlattices on appropriately miscut (001) InP substrates is shown to alter the microstructure of composition modulation from a 2D organization of short compositionally enriched wires to a single dominant modulation direction and wire lengths up to {approximately}1 {micro}m. The effects of miscut are interpreted in terms of surface step orientation and character. The material is strongly modulated and exhibits intense optical emission. The 1D modulations appear… more
Date: March 23, 2000
Creator: Follstaedt, David M.; Norman, A. G.; Reno, John L.; Jones, Eric D.; Twesten, R. D.; Lee, Stephen R. et al.
Partner: UNT Libraries Government Documents Department
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Generation of high-power, subpicosecond, submillimeter radiation for applications in novel device development and materials research

Description: This research exploits the high-energy, ultrafast laser technology and high voltage expertise at Los Alamos National Laboratory (LANL) to scale submillimeter-pulse generation with photoconducting antennas to large aperture sizes and high output powers. An experimental and theoretical approach was undertaken with a view towards optimizing the radiated output and determining the technology`s ultimate scalability. This is the final report of a three-year Laboratory-Directed Research and Developmen… more
Date: December 31, 1995
Creator: Taylor, A. J.; Roberts, J. P.; Kurnit, N. A.; Benicewicz, P. K.; Rodriquez, G.; Redondo, A. et al.
Partner: UNT Libraries Government Documents Department
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Ingaas/Inp Heterojunction Bipolar Transistors for Ultra-Low Power Circuit Applications

Description: For many modern day portable electronic applications, low power high speed devices have become very desirable. Very high values of f{sub T} and f{sub MAX} have been reported with InGaAs/InP heterojunction bipolar transistors (HBTs), but only under high bias and high current level operating conditions. An InGaAs/InP ultra-lowpower HBT with f{sub MAX} greater than 10 GHz operating at less than 20 {micro}A has been reported for the first time in this work. The results are obtained on a 2.5 x 5 {mi… more
Date: August 1, 1998
Creator: Chang, P. C.; Baca, A. G.; Hafich, M. J. & Ashby, C. I.
Partner: UNT Libraries Government Documents Department
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New approaches for high-efficiency solar cells. Final report

Description: This report summarizes the activities carried out in this subcontract. These activities cover, first the atomic layer epitaxy (ALE) growth of GaAs, AlGaAs and InGaP at fairly low growth temperatures. This was followed by using ALE to achieve high levels of doping both n-type and p-type required for tunnel junctions (Tj) in the cascade solar cell structures. Then the authors studied the properties of AlGaAs/InGaP and AlGaAs/GaAs tunnel junctions and their performances at different growth conditi… more
Date: December 1, 1997
Creator: Bedair, S. M. & El-Masry, N. A.
Partner: UNT Libraries Government Documents Department
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