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III-nitride based quantum wells (QWs) have been extensively studied as active buildings blocks for different electronic and optoelectronic devices. Several samples of GaN/AlN axial multi quantum well nanowires (MQW NWs) have been synthesized, leading to NWs with a MQW structure with GaN wells of different widths along the growth axis, 1.5, 2, 3 and 4 nm. In this work structural and optical properties...
Band lineup is one of the most important parameters associated with carrier confinement in heterostructures. Relations for computing the band line-ups of AlxGa1-xN based heterostructures have been developed. The band positions for AlxGa1-xN/GaN heterointerfaces are calculated from the equations developed, which directly co-relate the positions of the bands with the strain at the interface. The strains...
We investigated the effects of prestrained layers on piezoelectric fields and indium incorporation in blue-emitting InGaN/GaN quantum wells by using reverse-biased electroreflectance spectroscopy. We compared two sets of samples, which have identical structures except an insertion of an additional UV quantum well at the bottom of the blue-quantum well. Indium composition of quantum wells with the...
The effects etching depths of nanohole arrays close to or penetrate the quantum well structures are studied. Our results suggest that when the hole depth is close to the quantum well region, the surface states pinning reduces the band bending and leads to a blue shift of the emission spectrum. When the hole penetrates the quantum well region, similar effects are observed but are due to the strain...
We have developed a natural lithography method to fabricate nanorod structure. The spin-on glass is used as a space layer to realize the nanorod LED. The strain is released in nanorod structured LED which is indicated by their nearly constant electroluminescent peak wavelength at the injection current range between 25 mA and 100 mA. Furthermore, a highly concentrated radiation profile is observed...
This paper reports the first direct tensile test on a nearly defect free, n-type (Si-doped) GaN nanowire single crystal. Here, for the first time, nanowires have been integrated with actuated, active microelectromechanical (MEMS) structures using dielectrophoresis-driven self-assembly and Pt-C clamps created using a gallium focused ion beam. The nanowire modulus of elasticity is measured to be 201...
In this paper, we studied a method to reduce the compressive strain in the InGaN/GaN multiple quantum well (MQW) structures by inserting a strain relief layer between n-GaN and MQWs. The improvements in the interface quality and the optical properties were investigated by photoluminescence (PL) and high-resolution X-ray diffraction (HRXRD) analysis. The samples showed S-shaped emission energy peak...
Artykuł omawia zagadnienia związane z możliwościami jakie daje spektroskopia mikrbramanowska w analizie warstw epitaksjalnych azotku galu: wyznaczanie naprężeń i rozkładu naprężeń oraz odkształcenia w strukturach epitaksjalnych, a tym samym określenie jakości kryształu powierzchniowego. Możliwość jakościowej i ilościowej analizy wynika z faktu, że widmo Ramana jest charakterystyczne dla danego rodzaju...
We present a practical process to fabricate InGaN/GaN multiple-quantum-well nanorod structure. The nanorod light emitting diode array is realized by using monolayer silica nano-particle as nano-mask to define nanorod structure and a space layer to prevent p-type contact from connecting n-type GaN. The quantum confine stark effect is suppressed in nanorod device which is proved by electroluminescence...
A multi-physics multi-scale modeling platform has been developed and it has been applied to various stages of the LED manufacturing such as MOCVD reactor design, epitaxial growth based on silicon wafer, chip design and manufacturing, module packaging and assembly, and specific lamps. Discussions are also given to the ultra-scalable reactor design, material constitutive modeling, and curvature evolution...
Spinodal decomposition of the GaSbxNyAs1-x-y quaternary alloys lattice-matched to the GaAs as the result of the internal deformation and coherency strain energies is described. The alloys are represented as quasiternary regular solutions. The internal deformation energy is presented by the interaction parameters between the constituent compounds estimated within the framework of the valence force...
Our simulations and experiments demonstrate a new physical mechanism for detecting acoustic waves of THz frequencies. Detectable THz-frequency radiation is generated when the acoustic wave passes a piezoelectric interface.
HRTEM observation was conducted to find evidence of physical degradation in AlGaN/GaN heterostructure HEMT devices after life time testing. A strong relationship between electrical degradation and defects formation near the gate edge was observed. Detailed features of physical damages correlated with the degradation mechanism were discussed.
200 nm thick InxAl1-xN epilayers around lattice-matched to GaN were grown on GaN templates by MOCVD. The elastic strain, surface morphology and crystalline quality of the InxAl1-xN were evaluated by high resolution X-ray diffraction (HRXRD) measurements, scanning electron microscopy (SEM) images and Rutherford backscattering spectroscopy (RBS) analyses. The strain effect, as while as the influences...
Optical properties of 530 nm strain-compensated InGaN/InGaN/ZnO quantum well (QW) light-emitting diodes (LEDs) using a ZnO substrate are investigated using the multiband effective mass theory. These results are compared with those of conventional InGaN/GaN QW LEDs using a GaN substrate. A strain-compensated QW structure is found to have much larger spontaneous emission than a InGaN/GaN QW structure...
Quantum dot (QD) systems based on III-nitride have recently shown to be very promising nanostructures for high-quality light emitters. In this work, electronic and transport properties of AlN/GaN QDs are investigated by means of the TIBERCAD software tool, which allows both a macroscopic and an atomistic approach, with the final aim to couple them in a multiscale simulation environment.
The IQE of InGaN quantum-wells emit from green to red is not so high due to spatial separation of electrons and holes by strain-induced piezo-electric-field. The strain relaxation in InGaN-QWs by nano etching is discussed.
Deep Level Transient Spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS) have been used to distinguish the difference between electrically active point and extended defects in MOVPE-grown n-type GaN. Three dominant features are observed in the conventional DLTS spectrum, with energies in the region of 40 meV, 550 meV and 1.46 eV. However, detailed examination with LDLTS shows that all these...
For several decades, the output from semiconductor manufacturers has been high volume products with process optimisation being continued throughout the lifetime of the product to ensure a satisfactory yield. However, product lifetimes are continually shrinking to keep pace with market demands. Furthermore there is an increase in dasiafoundrypsila business where product volumes are low; consequently...
Multilayer of InAs QD with thin spacer thickness using GaNAs stress compensation layers (SCL) was investigated for the purpose of high modal gain. Multilayer up to 5 layers with 18 nm thin spacer thickness was realized in 1.4 um wavelength range without degradation of optical quality. This result indicates advantage of GaNAs spacer for multi stacking with thin spacer layer thickness.
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