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  • 1
    Electronic Resource
    Electronic Resource
    Optically pumped GaN/Al0.1Ga0.9N double-heterostructure ultraviolet laser (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2148-2150 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular-beam epitaxy was used to grow a 100 nm Al0.1Ga0.9N/100 nm GaN/500 nm Al0.1Ga0.9N double heterostructure on a 10-μm-thick GaN buffer layer grown with hydride vapor phase epitaxy on (0001) sapphire. Lasing from the 100 nm GaN active layer has been obtained at ∼359 nm at liquid-nitrogen temperature (77 K) and at ∼365 nm at room temperature (295 K), using transverse optical pumping at 337.1 nm with a 600 ps transversely excited atmospheric pressure pulsed nitrogen laser. Threshold pump fluences were measured to be 0.3 and 0.5 mJ/cm2 at 77 and 295 K, respectively, for a laser with 65 μm cavity length. In a laser of 23 μm cavity length, longitudinal cavity modes were observed with 0.56 nm spacing, corresponding to a group refractive index of 5.0 at the lasing wavelength. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361044
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  • 2
    Electronic Resource
    Electronic Resource
    Growth of gallium nitride by electron-cyclotron resonance plasma-assisted molecular-beam epitaxy: The role of charged species (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4587-4595 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of ionic and nonionic excited species of nitrogen in the growth of GaN thin films by electron-cyclotron resonance (ECR) plasma-assisted molecular-beam epitaxy has been investigated. It was found that the kinetics of film growth is significantly affected by the microwave power in the ECR discharge. Specifically, a transition from the island to a layer-by-layer and, finally, to a three-dimensional growth has been observed as a function of power. These morphological changes are accompanied by degradation of the electrical and luminescence properties, a result attributable to increased native defects and impurities. Secondary-ion-mass spectroscopic (SIMS) analysis indicates that impurity levels in the films increase with the plasma power levels used during the growth. To study the relative role of ion-induced native defects in these films, strategies for charged species extraction were developed by using an off-axis solenoid to modify the magnetic environment during growth. Films grown under a reduced ionic/excited neutral ratio environment show marked improvement in the electrical and luminescence properties. These data, together with SIMS analysis, indicate that observed improvements in these films are due to a reduction of native defects and not impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357293
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  • 3
    Electronic Resource
    Electronic Resource
    Light scattering in high-dislocation-density GaN (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1665-1667 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light scattering by edge dislocations and the resulting loss coefficient have been modeled for GaN layers. Phase-front deformation caused by the refractive-index variation in the dislocation's strain field has been considered and the resulting scattering loss calculated. We show that the high dislocation densities observed in recent GaN layers can result in significant large loss coefficients. The present work also offers some insights for improved lasers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117021
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  • 4
    Electronic Resource
    Electronic Resource
    Electron transport mechanism in gallium nitride (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 72-74 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron transport mechanism in autodoped gallium nitride films grown by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy was investigated by studying the temperature dependence of the Hall coefficient and resistivity on samples with various concentrations of autodoping centers. The Hall coefficients go through a maximum as the temperature is lowered from 300 K and then saturate at lower temperatures. The resistivities in the same temperature range initially increase exponentially and then saturate at lower temperatures. These findings are accounted for if a significant fraction of electron transport, even at room temperature, takes place in the autodoping centers and that conduction through these centers becomes dominant at lower temperatures. The activation energy of these centers was found to be on the order of 20–30 meV. When the concentration of the autodoping centers becomes smaller than that of deep compensating defects, the material becomes semi-insulating and transport by hopping in the compensating defects becomes dominant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108823
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  • 5
    Electronic Resource
    Electronic Resource
    Epitaxial growth of zinc blende and wurtzitic gallium nitride thin films on (001) silicon (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 944-946 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zinc blende and wurtzitic GaN films have been epitaxially grown onto (001)Si by electron 〈m1;&1p〉cyclotron resonance microwave plasma-assisted molecular beam epitaxy, using a two-step growth process. In this process a thin buffer layer is grown at relatively low temperatures followed by a higher temperature growth of the rest of the film. GaN films grown on a single crystalline GaN buffer have the zinc blende structure, while those grown on a polycrystalline or amorphous buffer have the wurtzitic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106309
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrogenation of p-type gallium nitride (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2264-2266 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hole concentrations of up to 1019 cm−3 have been reported for GaN:Mg films grown by molecular beam epitaxy without any post-growth treatment. Comparing results from Hall measurements and secondary ion mass spectrometry, we observe doping efficiencies of up to 10% at room temperatures in such p-type material. By hydrogenating at temperatures above 500 °C, the hole concentration can be reduced by an order of magnitude. A new photoluminescence line at 3.35 eV is observed after this treatment, both in p-type and unintentionally doped n-type material, which suggests the introduction of a hydrogen-related donor level in GaN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111639
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  • 7
    Electronic Resource
    Electronic Resource
    Blue-violet light emitting gallium nitride p-n junctions grown by electron cyclotron resonance-assisted molecular beam epitaxy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 268-270 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Blue-violet gallium nitride (GaN) light emitting p-n junctions were grown by the method of electron cyclotron resonance-assisted molecular beam epitaxy. This method has been modified to minimize plasma induced defects. Contrary to similar devices grown by metalorganic chemical vapor deposition, these devices do not require any postgrowth annealing to activate the Mg acceptors in the p layer. These devices turn-on at approximately 3 V and have a spectral emission peaking at 430 nm. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113513
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  • 8
    Electronic Resource
    Electronic Resource
    Intensity dependence of photoluminescence in GaN thin films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 336-338 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the intensity dependence of band-gap and midgap photoluminescence in GaN films grown by electron cyclotron resonance (ECR) microwave plasma-assisted molecular beam epitaxy. We find that the band-gap luminescence depends linearly while the midgap luminescence has a nonlinear dependence on the incident light intensity. These data were compared with a simple recombination model which assumes a density of recombination centers 2.2 eV below the conduction band edge. The concentration of these centers is higher in films grown at higher microwave power in the ECR plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111968
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  • 9
    Electronic Resource
    Electronic Resource
    Electronic and structural properties of GaN grown by hydride vapor phase epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 242-244 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic and structural properties of GaN were investigated for heteroepitaxial layers grown by hydride vapor phase epitaxy. Uniform film nucleation on the sapphire substrates was facilitated by a GaCl pretreatment. The films were all unintentionally doped n type. Variable temperature Hall effect measurements reveal electron concentrations as low as 2×1017 cm−3 and electron mobilities as high as 460 cm2/V s at 300 K. The films exhibit bound exciton photoluminescence lines with a full width at half-maximum (FWHM) of 2.42 meV at 2 K. Transmission electron microscopy studies of the GaN/sapphire interface reveal a ∼200 nm thick, highly defective GaN layer consisting predominantly of stacking faults. The excellent quality of these GaN films is attributed to this "auto-buffer'' layer which enables growth of GaN cells with a dislocation density of ∼3×108 cm−2 after ∼12 μm of film growth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117937
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  • 10
    Electronic Resource
    Electronic Resource
    Strongly localized excitons in gallium nitride (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2556-2558 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on strong excitonic luminescence in wurtzite GaN at 3.309 and 3.365 eV (T=6 K). These lines lie well below the band gap and are found commonly in layers grown by different techniques and on different substrates. From detailed photoluminescence investigations we find small thermal activation energies and a very weak electron–phonon coupling. The photoluminescence behavior under hydrostatic pressure is indicative of strongly localized defects. These findings are similar to observations of excitons localized at extended defects such as dislocations in II–VI compounds. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116182
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