Showing papers by "Thomas F. Kuech published in 2006"
TL;DR: Measurements using fluorescently labeled complementary and noncomplementary sequences show that the DNA-modified GaN surfaces exhibit excellent selectivity, while repeated cycles of hybridization and denaturation in urea show good stability.
Abstract: We demonstrate that photochemical functionalization can be used to functionalize and photopattern the surface of gallium nitride crystalline thin films with well-defined molecular and biomolecular layers. GaN(0001) surfaces exposed to a hydrogen plasma will react with organic molecules bearing an alkene (CC) group when illuminated with 254 nm light. Using a bifunctional molecule with an alkene group at one end and a protected amine group at the other, this process can be used to link the alkene group to the surface, leaving the protected amine exposed. Using a simple contact mask, we demonstrate the ability to directly pattern the spatial distribution of these protected amine groups on the surface with a lateral resolution of <12 μm. After deprotection of the amines, single-stranded DNA oligonucleotides were linked to the surface using a bifunctional cross-linker. Measurements using fluorescently labeled complementary and noncomplementary sequences show that the DNA-modified GaN surfaces exhibit excellent...
77 citations
TL;DR: In this paper, an alternate approach to self-assembly has been investigated for elimination of the wetting layer and achieving a uniform mono-modal QD size distribution on a GaAs substrate, hexagonally arranged uniform-sized QD arrays have been fabricated.
32 citations
TL;DR: In this article, thin layers (2-3nm) and high antimony-content (30%) GaAsSb were utilized for realizing satisfactory wave function overlap and long wavelength emission.
Abstract: Low temperature (30K) long wavelength photoluminescence emission (λ=1400–1600nm) from metalorganic chemical vapor deposition grown InGaAsN–GaAsSb type II “W” quantum wells (QWs), on GaAs substrates has been demonstrated. Thin layers (2–3nm) and high antimony-content (30%) GaAsSb were utilized in this study for realizing satisfactory wave function overlap and long wavelength emission. Tensile strained GaAsP barriers effectively improve the material structural and luminescence properties of the compressive strained active region. Room temperature photoluminescence data show that the type-II QW design is a promising candidate for realizing long wavelength GaAs-based diode lasers beyond 1500nm.
26 citations
Patent•
28 Dec 2006TL;DR: In this article, a dual waveguide heterostructure consisting of an optical waveguide contained within a larger THz waveguide layered structure is provided for a coherent guided wave of THz radiation.
Abstract: A THz radiation source comprising a dual waveguide heterostructure is provided The dual waveguide heterostructure includes an optical waveguide contained within a larger THz waveguide layered structure The radiation source provides a coherent guided wave of THz radiation which is generated via difference frequency mixing in a gain medium with a large second-order nonlinearity and propagated with low THz loss by a dielectric medium in the layered waveguide structure The THz radiation source is compact, has a high power output, and may be operated in continuous-wave (CW) mode at room temperature
24 citations
TL;DR: In this paper, the use of tensile strained barrier layers is found to significantly improve the photoluminescence intensity of the InGaAsN-GaAsSb type-II quantum well structure and result in a wavelength blueshift.
23 citations
TL;DR: In this paper, the dependence of the microstructure and morphology of InAs films, deposited on (1 − 0 − 0) GaAs substrates via metal-organic vapor-phase epitaxy (MOVPE), on growth parameters and the substrate miscut was studied.
17 citations
TL;DR: In this article, the growth mechanisms of GaSb in a metal-organic vapor-phase epitaxy (MOVPE) system were studied for both trimethyl gallium (TMG)/trimethyl antimony (TMSb) and triethyl gated gallium(TEG)/tMSb growth chemistries.
16 citations
TL;DR: In this article, temperature-dependent cavity length studies have been performed on multiple stack strain compensated InGaAs quantum-dot (QD) active region broad stripe laser structures grown by metal-organic chemical vapor deposition.
Abstract: Temperature-dependent cavity length studies have been performed on multiple stack strain compensated InGaAs quantum-dot (QD) active region broad stripe laser structures grown by metal-organic chemical vapor deposition. The characteristic temperature coefficients of the threshold current density (T/sub 0/) and external differential quantum efficiency (T/sub 1/) were calculated from variable temperature measurements. The correlation of the T/sub 0/,T/sub 1/ values and the extracted values of the characteristic temperature coefficients of the transparency current density, material gain, injection efficiency, and internal loss (T/sub tr/,T/sub g0/,T/sub /spl eta/inj/,T/sub /spl alpha/i/) from the temperature-dependent study is discussed. The T/sub 1/ values are higher than 400 K for five-stack QD laser structures, comparable values to conventional quantum-well (QW) laser structures. T/sub 0/ values are lower than 100 K. Extracted material gain parameters are found to increase with increasing temperature for the three-stack QD structure, and are nearly temperature independent for the five-stack structure, different to that observed in InGaAs QW lasers.
16 citations
TL;DR: In this article, a phenomenological methodology was used to characterize the intrinsic diffusion of tin in GaAs based on the coupled motion of substitutional and interstitial Sn atoms, which led to an anomalous double-profile diffusion curve observed in highly doped samples.
Abstract: A phenomenological methodology has been used to characterize the intrinsic diffusion of tin in GaAs based on the coupled motion of substitutional and interstitial Sn atoms. Both the rapid diffusivity of interstitial Sn atoms and their transformation to substitutionals by occupying gallium vacancies are processes that lead to an anomalous “double-profile” diffusion curve observed in highly doped samples. The model was developed for samples annealed over a range of 973–1123K. The model developed while developed and perhaps only applicable over this temperature range may be extendable to a larger temperature range provided that the underlying mechanism is unchanged. The methodology consists of using key aspects of the diffusion profiles along with the mass conservation criterion to predetermine bounds which prescribe the values of the parameters used to model the experimental data. This fitting procedure allowed for a more rapid assessment of the model parameters by providing physical bounds on their values ...
5 citations
01 Oct 2006
TL;DR: Incorporation of nitrogen into GaSbN/GaAsSb/InP quantum wells leads to bandgap narrowing and allows for GaAsN/GASB/I/INP type-II "W" QW structures with potential of achieving emission in the 2-3?m wavelength region as discussed by the authors.
Abstract: Incorporation of nitrogen into GaAsSb/InP quantum wells leads to bandgap narrowing and allows for GaAsSbN/GaAsSb/InP type-II "W" QW structures with potential of achieving emission in the 2-3 ?m wavelength region.
4 citations
Patent•
13 Sep 2006TL;DR: In this article, a point-of-use precursor for silane gas is presented, which is cyclohexadien-2,4-ylsilane, an air-stable liquid that can be thermolyzed in a pyrolysis process to efficiently generate high purity silane gases.
Abstract: Silane gas precursor compounds having the formula (I): wherein R1, R2, and R3 each can independently be hydrogen or halogen and wherein the cyclohexadiene ring can have one or more substituents selected from the group consisting of a saturated or unsaturated, straight chain or branched alkyl group, a halogen, NO2, and C≡N are disclosed. In one form, the silane gas precursor compound is cyclohexadien-2,4-ylsilane, an air-stable liquid, that can be thermolyzed in a pyrolysis process to efficiently generate high purity silane gas. The compounds of the present invention can thus serve as a “point-of-use” precursor for silane gas.
21 May 2006
TL;DR: In this paper, a 3-stage active regions exhibit emission that is blue-shifted from the PL, due to charge separation and higher-energy transitions, and they are grown by MOCVD.
Abstract: InGaAsN/GaAsSb dasiaWpsila type-II strain compensated quantum well lasers on GaAs substrates are grown by MOCVD. Preliminary lasers with 3-stage active regions exhibit emission that is blue-shifted from the PL, due to charge separation and higher-energy transitions.