In spite of the great progress in III-N technology, LEDs with wavelength >530
nm still exhibit low efficiency compared to blue and short-wavelength-green LEDs. Here we report on significant ...improvement of deep-green LED properties by modifications of the structure design. The combination of InGaN/GaN superlattice followed by low-temperature GaN is the key element to increase the electroluminescence efficiency for deep-green LED. Various techniques were employed to clarify the correlation between structure properties, growth regimes and design. Modification of the defect structure of the GaN buffer by InGaN layers appears to be mostly responsible for the observed effect. LEDs processed and assembled in a standard flip-chip geometry with Ni–Ag
p-contact demonstrate external quantum efficiencies of 8–20% in the 560–530
nm range.
The selective epitaxial growth of GaN by metalorganic vapor-phase epitaxy combined with ion-beam etching is investigated. To this end, partially masked GaN epitaxial layers are fabricated by ...depositing a thin Si
3
N
4
layer onto the surface in a single technological process with the growth of GaN and the subsequent opening of windows of different shapes in this layer by an ion beam. Selective epitaxial growth regimes are studied. It is shown that, in a situation where the total area of the windows in the mask is small relative to the total area of the sample, the required epitaxy duration should be 5–10 s, which impairs the reproducibility of the parameters of the epitaxial process. It is also shown that the mechanism of the selective growth of submicrometer objects differs significantly from that for planar layers and selectively grown layers with dimensions of ~1 μm or greater. The effect of precursor (trimethylgallium and ammonia) fluxes on the character of selective epitaxy is examined. To investigate the possibilities of varying mask topology for fabricating model objects with regard to photonic crystals, the impact of the shape and orientation of the windows in the Si
3
N
4
mask on the character of selective epitaxy is studied.
Optical properties of the resonant Bragg heterostructures with 10 and 30 GaN/AlGaN quantum wells were studied. The increasing of reflectivity at the resonance wavelength under condition of the Bragg ...wavelength and optical transition wavelength matching was observed experimentally at room temperature. The computer simulation of the optical transition wavelength in quantum wells and the optical reflectivity spectra at different reverse bias was implemented to evaluate radiative and non-radiative broadening parameters of the exciton in GaN/AlGaN quantum wells.
Influence of hydrogen on the growth of III-nitride materials by MOVPE is discussed using modeling and experimental study. The main conclusion, coming from the modeling and supported by numerous ...experimental observations, is that hydrogen affects the growth of III-nitrides in two different ways: via layer etching at elevated temperatures and via surface coverage with metal adatoms. The adatoms are found to accumulate on the surface due to interaction with hydrogen in a wide temperature range, including reduced temperatures. With regard to these effects, one can control such important characteristics as layer composition, growth anisotropies, surface quality, and even material properties (like p-doping level) by adjusting the carrier gas composition and other growth parameters.
Authors represent utilizing UHV Ga FIB for preparing a Si3N4/GaN substrate for submicron selective-area epitaxy. In result, GaN submicron stripes were grown in the 100, 200 and 500 nm windows of a ...Si3N4 mask layer. SEM investigations show good crystalline perfection of the grown stripes.
The epitaxial growth of InAlN layers and GaN/AlN/InAlN heterostructures for HEMTs in growth systems with horizontal reactors of the sizes 1 × 2", 3 × 2", and 6 × 2" is investigated. Studies of the ...structural properties of the grown InAlN layers and electrophysical parameters of the GaN/AlN/InAlN heterostructures show that the optimal quality of epitaxial growth is attained upon a compromise between the growth conditions for InGaN and AlGaN. A comparison of the epitaxial growth in different reactors shows that optimal conditions are realized in small-scale reactors which make possible the suppression of parasitic reactions in the gas phase. In addition, the size of the reactor should be sufficient to provide highly homogeneous heterostructure parameters over area for the subsequent fabrication of devices. The optimal compositions and thicknesses of the InAlN layer for attaining the highest conductance in GaN/AlN/InAlN transistor heterostructures.
The series of InAlGaN LED structures containing two different quantum wells emitting at wavelengths of ∼ 430 nm and ∼ 490 nm was grown. The influence of the quantum wells order, thickness of the ...barrier between the wells and its doping level on the optical properties was studied by photo- and electro-luminescence measurements. It was found that the quantum well with longer-wavelength emission is preferable to be located farther from a player than the shorter-wavelength quantum well to obtain emission from both QWs. Variation of the thickness of the barrier between the QWs and its doping level allows controlling the intensity ratio of two emission peaks.
High electron mobility transistors (HEMTs) technologies based on AlGaN/GaN and InAlN/GaN heterostructures have been developed. The research focused on influence of epitaxial growth conditions and ...buffer doping profiles on electrical properties HEMTs. An output power density of 4W/mm at 17 GHz was demonstrated for InAlN/GaN HEMTs and 7W/mm at 10 GHz for AlGaN/GaN HEMTs.
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