Toward defect-free semi-polar GaN templates on pre-structured sapphire

The microstructure of semi-polar (11–22) GaN templates grown on pre-structured r-plane sapphire by MOVPE has been characterized by TEM. Cross-sectional observations indicate that defects are generated in three regions of the layers: threading dislocations at the inclined GaN/sapphire interface, basal plane stacking faults (BSFs) at the c−-wing, BSFs and threading dislocations at the coalescence between neighboring GaN stripes. An in situ SiN interlayer deposited at an early stage of the growth is shown to be effective in blocking the propagation of dislocations, which is mainly attributed to SiN formed on the c-plane rather than on the (11–22) plane. Si-doped marker layers have been used to study the evolution of the growth front before coalescence as a function of temperature. A high growth temperature is associated with the formation of highly faceted GaN stripes. Dislocations originally running along the c-direction are bent to the [11–20] direction driven by a progressing (11–22) facet. An efficient defect reduction is realized as a result of terminating these dislocations at voids partially defined by the (11–20) facet

Filtering of Defects in Semipolar (11−22) GaN Using 2-Steps Lateral Epitaxial Overgrowth

Good-quality (11−22) semipolar GaN sample was obtained using epitaxial lateral overgrowth. The growth conditions were chosen to enhance the growth rate along the [0001] inclined direction. Thus, the coalescence boundaries stop the propagation of basal stacking faults. The faults filtering and the improvement of the crystalline quality were attested by transmission electron microscopy and low temperature photoluminescence. The temperature dependence of the luminescence polarization under normal incidence was also studied

Selective area growth of a- and c-plane GaN nanocolumns by molecular beam epitaxy using colloidal nanolithography

Selective area growth of a-plane GaN nanocolumns by molecular beam epitaxy was performed for the first time on a-plane GaN templates. Ti masks with 150 nm diameter nanoholes were fabricated by colloidal lithography, an easy, fast and cheap process capable to handle large areas. Even though colloidal lithography does not provide a perfect geometrical arrangement like e-beam lithography, it produces a very homogeneous mask in terms of nanohole diameter and density, and is used here for the first time for the selective area growth of GaN. Selective area growth of a-plane GaN nanocolumns is compared, in terms of anisotropic lateral and vertical growth rates, with GaN nanocolumns grown selectively on the c-plan

Cleaved-facet violet laser diodes with lattice-matched Al0.82In0.18N/GaN multilayers as n-cladding

Electrically injected, edge-emitting cleaved-facet violet laser diodes were realized using a 480 nm thick lattice matched Si doped Al0.82In0.18N/GaN multilayer as the cladding on the n-side of the waveguide. Far-field measurements verify strong mode confinement to the waveguide. An extra voltage is measured and investigated using separate mesa structures with a single AlInN insertion. This showed that the electron current has a small thermally activated shunt resistance with a barrier of 0.135 eV and a current which scales according to V-n, where n similar to 3 at current densities appropriate to laser operation. (C) 2011 American Institute of Physics. (doi:10.1063/1.3589974

Ordered gan/ingan nanorods arrays grown by molecular beam epitaxy for phosphor-free white light emission

The basics of the self-assembled growth of GaN nanorods on Si(111) are reviewed. Morphology differences and optical properties are compared to those of GaN layers grown directly on Si(111). The effects of the growth temperature on the In incorporation in self-assembled InGaN nanorods grown on Si(111) is described. In addition, the inclusion of InGaN quantum disk structures into selfassembled GaN nanorods show clear confinement effects as a function of the quantum disk thickness. In order to overcome the properties dispersion and the intrinsic inhomogeneous nature of the self-assembled growth, the selective area growth of GaN nanorods on both, c-plane and a-plane GaN on sapphire templates, is addressed, with special emphasis on optical quality and morphology differences. The analysis of the optical emission from a single InGaN quantum disk is shown for both polar and non-polar nanorod orientation

Advances on MBE selective area growth of III-nitride nanostructures: from nanoLEDs to pseudo substrates

The aim of this work is to provide an overview on the recent advances in the selective area growth (SAG) of (In)GaN nanostructures by plasma assisted molecular beam epitaxy, focusing on their potential as building blocks for next generation LEDs. The first three sections deal with the basic growth mechanisms of GaN SAG and the emission control in the entire ultraviolet to infrared range, including approaches for white light emission, using InGaN disks and thick segments on axial nanocolumns. SAG of axial nanostructures is eveloped on both GaN/sapphire templates and GaN-buffered Si(111). As an alternative to axial nanocolumns, section 4 reports on the growth and characterization of InGaN/GaN core-shell structures on an ordered array of top-down patterned GaN microrods. Finally, section 5 reports on the SAG of GaN, with and without InGaN insertion, on semi-polar (11-22) and non-polar (11-20) templates. Upon SAG the high defect density present in the templates is strongly reduced as indicated by a dramatic improvement of the optical properties. In the case of SAG on nonpolar (11-22) templates, the formation of nanostructures with a low aspect ratio took place allowing for the fabrication of high-quality, non-polar GaN pseudo-templates by coalescence of these nanostructures

Influence of substrate type and orientation on the morphology and optical properties of selective area growth of GaN and InGaN nanocolumns

A relevant issue concerning optoelectronic devices based on III-nitrides is the presence of strong polarization fields that may reduce efficiency

Etude de l'hydrogenation photocathodique de Si(p) dans l'acide fluorhydrique HF 5%

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Croissance et propriétés optiques et structurales de nitrures semipolaires (11-22) hétéroépitaxiés sur saphir

Ce travail de thèse concerne la croissance épitaxiale par MOVPE et l étude de nitrures d orientation semipolaire (11-22) sur saphir. Des couches de grande qualité cristalline ont été obtenues en utilisant deux techniques. La première est un procédé original d épitaxie latérale (ELO) : en favorisant la croissance selon [0001], les fautes d empilement sont arrêtées au niveau du joint de coalescence. La seconde technique consiste en l utilisation d un substrat de saphir plan r gravé par voie chimique : la nucléation s effectue au niveau de micro-facette c, ainsi peu de défauts sont créés. Une couche ELO a été étudiée par photoluminescence (PL) et réflectivité en polarisation et en température. Le GaN est polarisé selon [1-100]. Les calculs en théorie k.p ont permis de retrouver les résultats PL. D autre part des couches (In,Ga)N polaires et semipolaires ont été élaborées. L analyse SIMS montre que l incorporation d indium est plus grande dans les couches semipolaires. Ces dernières présentent un fort décalage de Stokes tandis que celui des couches polaires est très faible. Les résultats sur les puits quantiques (In,Ga)N/GaN épitaxiés sur tremplin GaN et GaN ELO montrent que l ELO apporte une amélioration d un facteur 3 sur l intensité d émission, faible en comparaison de la très forte réduction des défauts dans le GaN. Pour des compositions en indium importante, les puits sont polarisés selon [11-2-3], comme le montrent des calculs. Puis des nanostructures de GaN sur (Al,Ga)N émettant dans l UV ont été déposées par épitaxie par jets moléculaires (MBE) sur des tremplins de GaN. Enfin des LEDs semipolaires émettant du vert au rouge ont été étudiées par électroluminescence.NICE-BU Sciences (060882101) / SudocSudocFranceF

Band edge versus deep luminescence of InxGa1-xN layers grown by molecular beam epitaxy

InxGa1-xN (0<x<0.2) thin layers were grown on GaN-coated sapphire substrates by molecular beam epitaxy (MBE) using ammonia as the nitrogen source. Their optical properties have been investigated by low- and room-temperature photoluminescence (PL) and photothermal deflection spectroscopy. It is shown that high-quality InxGa1-xN layers with x similar to 0.1 can be grown by MBE using NH3. The PL linewidths are 48 and 80 meV at 9 and 300 K, respectively. A bowing parameter of 1 eV is deduced for the band-edge luminescence energy. On the other hand, when the growth conditions slightly move aside the optimum, the PL spectra exhibit broad and deep luminescence. The variation of the PL energy of this deep luminescence as a function of the In composition is then discussed. (C) 1998 American Institute of Physics