Damien Salomon

M-Plane Core-Shell InGaN/GaN Multiple-Quantum-Wells on GaN Wires for Electroluminescent Devices

Nonpolar InGaN/GaN multiple quantum wells (MQWs) grown on the {11-00} sidewalls of c-axis GaN wires have been grown by organometallic vapor phase epitaxy on c-sapphire substrates. The structural properties of single wires are studied in detail by scanning transmission electron microscopy and in a more original way by secondary ion mass spectroscopy to quantify defects, thickness (1-8 nm) and In-composition in the wells (∼16%). The core-shell MQW light emission characteristics (390-420 nm at 5 K) were investigated by cathodo- and photoluminescence demonstrating the absence of the quantum Stark effect as expected due to the nonpolar orientation. Finally, these radial nonpolar quantum wells were used in room-temperature single-wire electroluminescent devices emitting at 392 nm by exploiting sidewall emission.

Single-wire photodetectors based on InGaN/GaN radial quantum wells in GaN wires grown by catalyst-free metal-organic vapor phase epitaxy

We present a letter on single-wire photodetectors based on radial n-i-n multiquantum well (QW) junctions. The devices are realized from GaN wires grown by catalyst-free metalorganic vapor phase epitaxy coated at their top by five nonpolar In0.16Ga0.84N/GaN undoped radial QWs, and are sensitive to light with energy E>2.6 eV. Their photoconductive gain is as high as 2×103. The scanning photocurrent microscopy maps evidence that the detector response is localized at the extremity containing the QWs for both below (at λ=488 nm) and above GaN band gap (at λ=244 nm) excitation. This confirms that the device operates as a radial n-i-n junction.

Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN Quantum Wells

Single-wire light-emitting diodes based on radial p–i–n multi quantum well (QW) junctions have been realized from GaN wires grown by catalyst-free metal organic vapor phase epitaxy. The InxGa1-xN/GaN undoped QW system is coated over both the nonpolar lateral sidewalls and on the polar upper surface. Cathodo- and electroluminescence (EL) experiments provide evidence that the polar QWs emit in the visible spectral range at systematically lower energy than the nonpolar QWs. The EL of the polar or nonpolar QWs can be selectively activated by varying the sample temperature and current injection level.

Metal organic vapour-phase epitaxy growth of GaN wires on Si (111) for light-emitting diode applications

GaN wires are grown on a Si (111) substrate by metal organic vapour-phase epitaxy on a thin deposited AlN blanket and through a thin SiNx layer formed spontaneously at the AlN/Si interface. N-doped wires are used as templates for the growth of core-shell InGaN/GaN multiple quantum wells coated by a p-doped shell. Standing single-wire heterostructures are connected using a metallic tip and a Si substrate backside contact, and the electroluminescence at room temperature and forward bias is demonstrated at 420 nm. This result points out the feasibility of lower cost nitride-based wires for light-emitting diode applications.

Silane-Induced N-Polarity in Wires Probed by a Synchrotron Nanobeam

Noncentrosymmetric one-dimensional structures are key driving forces behind advanced nanodevices. Owing to the critical role of silane injection in creating nanosized architectures, it has become a challenge to investigate the induced local lattice polarity in single GaN wires. Thus, if axial and radial structures are well-grown by a silane-mediated approach, an ideal model to study their polar orientations is formed. By combining synchrotron X-ray fluorescence and X-ray excited optical luminescence, we show here experimental evidence of the role of silane to promote the N-polarity, light emission, and elemental incorporation within single wires. In addition, our experiment demonstrates the ability to spatially examine carrier diffusion phenomena without electrical contacts, opening new avenues for further studies with simultaneous optical and elemental sensitivity at the nanoscale.

Thin-Wall GaN/InAlN Multiple Quantum Well Tubes

Thin-wall tubes composed of nitride semiconductors (III-N compounds) based on GaN/InAlN multiple quantum wells (MQWs) are fabricated by metal-organic vapor-phase epitaxy in a simple and full III-N approach. The synthesis of such MQW-tubes is based on the growth of N-polar c-axis vertical GaN wires surrounded by a core-shell MQW heterostructure followed by in situ selective etching using controlled H2/NH3 annealing at 1010 °C to remove the inner GaN wire part. After this process, well-defined MQW-based tubes having nonpolar m-plane orientation exhibit UV light near 330 nm up to room temperature, consistent with the emission of GaN/InAlN MQWs. Partially etched tubes reveal a quantum-dotlike signature originating from nanosized GaN residuals present inside the tubes. The possibility to fabricate in a simple way thin-wall III-N tubes composed of an embedded MQW-based active region offering controllable optical emission properties constitutes an important step forward to develop new nitride devices such as emitters, detectors or sensors based on tubelike nanostructures.