Diffraction Properties and Application of 3D Polymer Woodpile Photonic Crystal Structure

We present a new technique for modification of diffraction and optical properties of photonic devices by surface application of polymer Three-Dimensional (3D) woodpile Photonic Crystal (PhC) structure. Woodpile structure based on IP-Dip polymer was designed and fabricated by Direct Laser Writing (DLW) lithography method based on nonlinear Two-Photon Absorption (TPA). At first, we investigated diffraction properties of woodpile structure with a period of 2 μm. The structure was placed on a glass substrate, and diffraction patterns were measured using laser sources with different wavelengths. After diffraction properties investigation, the fabricated structures were used in optoelectronic devices by their surface application. Our polymer 3D PhC woodpile structures were used for radiation properties modification of light emitting devices - optical fiber and Light Emitting Diode (LED) and for angular photoresponse modification of InGaAsN-based photodiode. The modification of the far-field radiation patterns of optical fiber and LED and spatial modulation of light coupling into photodiode chip with applied structures were measured by goniophotometer. Quality of fabricated structures was analyzed by a Scanning Electron Microscope (SEM)

Composition related electrical active defect states of InGaAs and GaAsN

This paper discusses results of electrically active defect states - deep energy level analysis in InGaAs and GaAsN undoped semiconductor structures grown for solar cell applications. Main attention is focused on composition and growth condition dependent impurities and the investigation of their possible origins. For this purpose a widely utilized spectroscopy method, Deep Level Transient Fourier Spectroscopy, was utilized. The most significant responses of each sample labelled as InG2, InG3 and NG1, NG2 were discussed in detail and confirmed by simulations and literature data. The presence of a possible dual conduction type and dual state defect complex, dependent on the In/N composition, is reported. Beneficial characteristics of specific indium and nitrogen concentrations capable of eliminating or reducing certain point defects and dislocations are stated

N coordination chemistry in diluted InGaAs nitride layers

GaAsN and InGaAsN semiconductor alloys with a small amount of nitrogen, so called dilute nitrides, constitute a novel compounds family with applications in telecom lasers and very efficient multijunction solar cells. The incorporation of N, which has a much larger electronegativity and smaller atomic size compared to As, induces a strong structural distortion in the InGaAs coordination chemistry, which will also affect the material electronic structure and band-gap. In particular, the nearest-neighbour bonding configuration of the N in InGaAsN has proven its influence on the band-gap. Our ARXPS results demonstrate that a higher growth temperature favour the formation of In-N bonds.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. - MINECO through TEC2011-28639-C02-02 and TEC2014-54260-C3-3-P - Wroclaw University of Technology statutory gran

GaInNas/GaAs QW Based Structures to Compensate Parasitic Effect of Quantum-Confined Stark Effect in Photodetector Applications

The inhomogeneities of multicomponent semiconductor alloys, as well as phase segregation, can be utilized for enhancement of photodetector absorption properties and thus its efficiency. In this paper, the influence of external electric field on the probability of light absorption in the GaInNAs quantum well is discussed. Both phenomenon: indium and nitrogen composition gradient as well as step-like quantum well are applied to design the QW with compensation of the Quantum-Confined Stark Effect (QCSE) Parasitic effect of QCSE results from decrease of the wave functions overlapping in the QWs placed in reverse biased junction, which finally decrease the efficiency of the photodetector

AP-MOVPE Technology and Characterization of InGaAsN p-i-n Subcell for InGaAsN/GaAs Tandem Solar Cell

Tandem (two p-n junctions connected by tunnel junction) and multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds and alloys are the most effective photovoltaic devices. Record efficiency of the MJSCs exceeds 44% under concentrated sunlight. Individual subcells connected in series by tunnel junctions are crucial components of these devices. In this paper we present atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE) of InGaAsN based subcell for InGaAsN/GaAs tandem solar cell. The parameters of epitaxial structure (optical and electrical), fabrication process of the test solar cell devices and current-voltage (J-V) characteristics are presented and discussed

Synthesis of New Perhydropyrrolo[1,2-a]pyrazine Derivatives and Their Evaluation in Animal Models of Epilepsy

A series of novel stereochemically pure derivatives of the investigative broad-spectrum anticonvulsant ADD408003 was designed and synthesized. Five-center four-component (U-5C-4CR) and four-center three-component (U-4C-3CR) variants of Ugi reaction were used in the key step of the synthetic pathways. The compounds obtained were evaluated for the anticonvulsant activitiy in the maximal electroshock seizure (MES), subcutaneous Metrazole (scMET) and minimal clonic seizure (6 Hz) animal models of epilepsy. The efficacies of most derivatives in the 6 Hz model of pharmacoresistant partial seizures were markedly higher than in the ‘classical’ MES and scMET models. The most active compounds, (4R,8aR)-3a, and (4S,8aS)-6 displayed median effective doses (ED50) of 47.90 and 126.19 mg/kg, respectively, for the 6 Hz test

STRUCTURAL CHARACTERIZATION OF DOPED THICK GaInNAs LAYERS ---AMBIGUITIES AND CHALLENGES

GaInNAs alloys are mostly used as an active part of light sources for long wavelength telecom applications. Beside this, these materials are used as thin quantum wells (QWs), and a need is to grow thick layers of such semiconductor alloys for photodetectors and photovoltaic cells applications. However, structural characterization of the GaInNAs layers is hindered by non-homogeneity of the In and N distributions along the layer. In this work the challenges of the structural characterization of doped thick GaInNAs layers grown by atmospheric pressure metalorganic vapour phase epitaxy (APMOVPE) will be presented

Influence of As-N Interstitial Complexes on Strain Generated in GaAsN Epilayers Grown by AP-MOVPE

This work presents an investigation of the fully strained GaAsN/GaAs heterostructures obtained by atmospheric pressure metalorganic vapor phase epitaxy, focusing on the analysis of the strain generated in the GaAsN epilayers and its correlation with the formation of split interstitial complexes (N-As)As. We analyzed strained GaAsN epilayers with nitrogen contents and thicknesses varying from 0.93 to 1.81% and 65 to 130 nm, respectively. The composition and thickness were determined by high resolution X-ray diffraction, and the strain was determined by Raman spectroscopy, while the N-bonding configurations were determined by X-ray photoelectron spectroscopy. We found that the strain generated in the GaAsN epilayers is mainly caused by a lattice mismatch with the GaAs substrate. This macroscopic strain is independent of the amount of (N-As)As interstitial defects, while the local strain, induced by an alloying effect, tends to decrease with an increasing ratio of (N-As)As interstitial defects to substitutional nitrogen atoms incorporated into an arsenic sublattice—NAs. Here, we show experimentally, for the first time, a correlation between the strain in the GaAsN epilayers, caused by an alloying effect determined by Raman spectroscopy, and the (N-As)As/NAs ratio estimated by the XPS method. We found out that the (N-As)As interstitials compensate the local strain resulting from the presence of N in the GaAs matrix, if their amount does not exceed ~65% of the substitutional introduced nitrogen NAs

DLTS Study of InGaAsN/GaAs p-i-n Diode

The paper presents an in-depth DLTS characterization of the p-i-n structure based on the InGaAsN/GaAs triple quantum well. Three DLTS evaluation methods were used for evaluation of the measured DLTS spectra. The results of all evaluation methods are compared and discussed. One of the evaluation methods that were used is a novel numerical algorithm that was recently developed. Several material and growth defects were identified. Emission from the quantum well was also observed and identified. The parameters of the energy levels were calculated and compared. The studied InGaAsN/GaAs structure is promising candidate for the solar cell applications and the further refinement of the growth process and technology is encouraged