Plane Sapphire (plane + sapphire)

Distribution by Scientific Domains

Terms modified by Plane Sapphire

  • plane sapphire substrate

  • Selected Abstracts


    Nanowire-Templated Epitaxial Growth: Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire (Adv. Mater.

    ADVANCED MATERIALS, Issue 23 2009
    23/2009)
    George Wang and co-workers report on p. 2416 that low dislocation density a -plane GaN films can be grown by the coalescence of vertically-aligned, single-crystalline GaN nanowires on lattice-mismatched r -plane sapphire. In this technique, shown by the artists' rendering on the inside cover, the nanowires facilitate dramatic strain relaxation in the suspended GaN film, leading to a large reduction in defects. [source]


    Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire

    ADVANCED MATERIALS, Issue 23 2009
    Qiming Li
    Coalescence of a vertically aligned GaN nanowire array on r -plane sapphire, a technique called nanowire-templated lateral epitaxial growth, is used to grow low-dislocation density a -plane GaN. The resulting film is connected to the lattice-mismatched substrate by nanowires, which facilitates dramatic strain relaxation and leads to a significant reduction in defects. [source]


    Recent Progress in GaN-Based Light-Emitting Diodes

    ADVANCED MATERIALS, Issue 45 2009
    Haiqiang Jia
    Abstract In the last few years the GaN-based white light-emitting diode (LED) has been remarkable as a commercially available solid-state light source. To increase the luminescence power, we studied GaN LED epitaxial materials. First, a special maskless V-grooved c -plane sapphire was fabricated, a GaN lateral epitaxial overgrowth method on this substrate was developed, and consequently GaN films are obtained with low dislocation densities and an increased light-emitting efficiency (because of the enhanced reflection from the V-grooved plane). Furthermore, anomalous tunneling-assisted carrier transfer in an asymmetrically coupled InGaN/GaN quantum well structure was studied. A new quantum well structure using this effect is designed to enhance the luminescent efficiency of the LED to ,72%. Finally, a single-chip phosphor-free white LED is fabricated, a stable white light is emitted for currents from 20 to 60,mA, which makes the LED chip suitable for lighting applications. [source]


    Nanowire-Templated Epitaxial Growth: Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire (Adv. Mater.

    ADVANCED MATERIALS, Issue 23 2009
    23/2009)
    George Wang and co-workers report on p. 2416 that low dislocation density a -plane GaN films can be grown by the coalescence of vertically-aligned, single-crystalline GaN nanowires on lattice-mismatched r -plane sapphire. In this technique, shown by the artists' rendering on the inside cover, the nanowires facilitate dramatic strain relaxation in the suspended GaN film, leading to a large reduction in defects. [source]


    Nanowire-Templated Lateral Epitaxial Growth of Low-Dislocation Density Nonpolar a -Plane GaN on r -Plane Sapphire

    ADVANCED MATERIALS, Issue 23 2009
    Qiming Li
    Coalescence of a vertically aligned GaN nanowire array on r -plane sapphire, a technique called nanowire-templated lateral epitaxial growth, is used to grow low-dislocation density a -plane GaN. The resulting film is connected to the lattice-mismatched substrate by nanowires, which facilitates dramatic strain relaxation and leads to a significant reduction in defects. [source]


    Highly a -axis oriented ,-LiAlO2 layer on a -plane sapphire fabricated by vapor transport equilibration

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2004
    Shengming Zhou
    Abstract A single-phase ,-LiAlO2 layer with a highly-preferred (100) orientation on sapphire substrate is successfully fabricated by vapor transport equilibration (VTE) technique in Li-rich ambient. The VTE treatment temperature is essential to obtaining the high-quality layer of ,-LiAlO2, and the optimized temperature is about 1050 C in the present work. It is promising to fabricate the ,-LIAlO2(100)//sapphire composite substrate for GaN-based epitaxial film. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Strong ultraviolet emission from non-polar AlGaN/GaN quantum wells grown over r -plane sapphire substrates

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
    W. H. Sun
    Abstract GaN and GaN/Al0.25Ga0.75N multiple quantum wells (MQWs) over c - and r -plane sapphire substrates have been grown by metal-organic chemical vapor deposition. A comparative study of photoluminescence (PL) in GaN epitaxial layers and AlGaN/GaN MQWs on these two types of substrates is reported. At low excitation levels, the measured room temperature PL signal in GaN layers grown over r -plane sapphire was more than order of magnitude lower than in GaN on c -plane substrates. In contrast, the emission intensity from AlGaN/GaN MQWs grown over r -plane substrates was almost 30 times stronger than in the structures grown over c -plane sapphire. Furthermore, with excitation power density up to 1 MW/cm2, the PL peak position for the non-polar MQWs kept completely stable whereas the one for the c -plane structures exhibited a blue shift as large as 250 meV. We attribute this large difference in the ultraviolet emission intensity to the suppression of a strong quantum Stark effect in the AlGaN/GaN MQWs on the r -plane sapphire. ( 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    GaN/Al0.5Ga0.5N quantum dots and quantum dashes

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2009
    Thomas Huault
    Abstract GaN/Al0.5Ga0.5N nanostructures grown on c -plane sapphire by molecular beam epitaxy using ammonia as N source have been studied. Depending on the ammonia pressure during the two dimensional , three dimensional transition of the GaN layer, the shape of the islands is strongly modified: elongated or isotropic islands are observed, leading to the formation of quantum dashes or quantum dots, respectively. This shape transition is seen as a consequence of a change in surface energy. The change of morphology of the GaN layer is clearly evidenced by photoluminescence measurements, and a large redshift in the emission peak is observed for quantum dashes as compared to quantum dots. An electric field ,3 MV/cm is estimated from the measurements at an excitation power ,20 mW/cm2. Weak photoluminescence quenching between low and room temperature for both QDs and QDashes structures is observed, indicating a strong confinement of carriers into the nanostructures. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    X-ray diffraction reciprocal lattice space mapping of a -plane AlGaN on GaN

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006
    Michinobu Tsuda
    Abstract In this study, the anisotropic strain in a -plane AlGaN on GaN was investigated by X-ray diffraction (XRD) analysis using AlGaN/GaN heterostructure grown on r -plane sapphire. An a -plane GaN layer is compressively strained, particularly in the m -axis direction. According to XRD reciprocal lattice space mapping, the AlGaN layer was strained under tensile stress and grown almost coherently to the underlying GaN layer. The tensile stress in the AlGaN layer in the c -axis direction is approximately 1.7 times larger than that in the m -axis direction. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Growth of GaN on a -plane sapphire: in-plane epitaxial relationships and lattice parameters

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
    T. Paskova
    Abstract We have studied GaN films grown on a -plane sapphire substrates by both hydride vapor phase epitaxy (HVPE) and metalorganic vapor phase epitaxy (MOVPE). The in-plane orientation relationships between the epitaxial films and the substrate are determined to be [11,20]GaN , [0001]sapphire and [1,100]GaN , [1,100]sapphire in the HVPE growth, while [1,100]GaN , [0001]sapphire and [11,20]GaN , [1,100]sapphire are found in the MOVPE growth. The different orientation preferences are attributed to the atom termination of the sapphire surface determined by the substrate treatment used in the different growth methods. The effect of the lattice matches on the in-plane lattice parameters and strain anisotropy in the two cases is studied. ( 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Structural and optical characterization of (11-22) semipolar GaN on m -plane sapphire without low temperature buffer layer

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010
    Sung-Nam Lee
    Abstract We reported the high quality semipolar (11-22) GaN grown on m-sapphire by using the novel two-step growth method without low temperature GaN or AlN buffer layer. It is found that macroscopic surface morphology of semipolar GaN epilayer was very smooth, while microscopic surface structure was arrowhead-like surface structure toward the direction of [1-21-1]. Anisotropic crystal properties of semipolar GaN/m-sapphire were also observed by two incident directions of X-ray beam. Therefore, we suggested that the anisotropic crystal properties and arrow-head like surface structure would be caused by heteroepitaxial crystallograhpic difference between semipolar GaN and m-sapphire. Additionally, photoluminescence (PL) measurements showed the strong bandedge emission of n-type semipolar GaN without yellow luminescence ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Selective area heteroepitaxy of low dimensional a -plane and c -plane InGaN nanostructures using pulsed MOCVD

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
    V. Jindal
    Abstract High density a -plane and c -plane InGaN nanostructures have been developed by nanoscale selective area epitaxial growth using pulsed MOCVD. SiO2 was used as a mask with nanopatterning through an anodic aluminum oxide template. The lateral dimensions of the pattern were controlled and varied from 30 nm to 180 nm by changing the anodization voltage and the electrolyte. Different substrates such as a -plane GaN on r -plane sapphire, r -plane sapphire and c -plane sapphire were used to develop InGaN nanostructures in a - and c - crystallographic directions respectively. Under identical growth conditions, InGaN nanostructures of various shapes were obtained on different substrates with differences in emission wavelength. The shape of the nanostructures on different substrates is discussed with respect to the stability and growth rates of various planes. However, the difference in emission wavelength is attributed to the In incorporation in the nanostructures. The optical properties of the nanostructures were studied by photoluminescence (PL) spectroscopy. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Microstructure of A -plane InN grown on R -plane sapphire by ECR-MBE

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
    S. Watanabe
    Abstract We used electron cyclotron resonance plasma-excited molecular beam epitaxy (ECR-MBE) to grow A -plane (110) InN on nitridated R -plane (102) sapphire and then measured the structural properties using transmission electron microscopy (TEM). We determined the epitaxial relationship between A -plane InN and R -plane sapphire to be (110)InN // (102)sapphire and [100]InN // [110]sapphire. Moreover, the results indicated that the nitridation of the sapphire produced a (001) cubic AlN layer, and this layer caused the subsequent InN to have its a-axis normal to the interface. Also, by using two diffraction vector orientations in the TEM measurement, we found that dislocations with a screw component had a density of about 5 1010 cm,2, which is about ten times higher than that with an edge component. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Growth of A -plane (11-20) In-rich InGaN on R -plane (10-12) sapphire by RF-MBE

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
    M. Noda
    Abstract Non-polar A -plane (11-20) high In content (In-rich) InGaN was grown on R -plane (10-12) sapphire with an InN template by radio-frequency plasma assisted molecular beam epitaxy (RF-MBE). Nitridation of R -plane sapphire was carried out at 300 C for 2 hours by RF-nitrogen plasma. A template of A -plane InN was grown at 400 C. The In-rich InGaN films were then grown at the same temperature on the InN template. We characterized the films using reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy (SEM) and photo-luminescence (PL). These results indicated clearly that non-polar In0.71Ga0.29N was successfully obtained with a PL emission at approximately 1.1 eV. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Morphological evaluation of epitaxial GaN grown on r -plane sapphire by metalorganic vapor-phase epitaxy

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006
    K. Kusakabe
    Abstract Morphological evaluation of epitaxial GaN films grown on r -plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy was investigated. The surface frequently showed rough morphology when the GaN was grown at conventional epitaxial conditions. It was found, however, that the surface roughness was improved by using appropriate combinations of growth temperature and low-temperature GaN buffer thickness. Thereby, a peak-to-valley value of the roughness was reduced from 4 ,m to 0.8 ,m. The rotation of crystallographic orientations was observed in the flattened GaN films. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]