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Methodology
The main purpose of this project to develop of the technology of the InGaAsN-GaN system. This includes the investigations of the growth of the system, basic structural, optical and electrical properties of the InGaAsN-GaN HSs, self-organization processes, device processing and studies of the device characteristics.
Growth.
Growth will start with investigations of the incorporation of the As atoms in the GaN. Influence of the growth parameters (temperature, growth rates, component pressure) on the quality of the InGaAsN layers will be studied and their optimization will be carried out. Acting of the As as surfactant on the GaN growth and properties of the GaN layers will be studied. It will be developed control introduction of the As atoms in GaN. Due to large difference between lattice constants of the GaAs and GaN attention to the growth of short-period InGaAsN-GaN superlattices will paid. This includes studies of the formation of the interfaces, influence of the growth interruptions on the properties of strain InGaAsN layer. Moreover, because strain can results in transformation of the InGaAsN layer to the QD array (that is typical for III-V system), role of these self-organized processes will be investigated. After development of the growth of InGaAsN-GaN system, design of the InGaAsN-based active region of LEDs will be carried out.
Characterization
Characterization will be follow the growth that provides rapid control of the parameters of the structures and their connection with growth parameters. It will include XRD, Auger electron microscopy, SIMS. Structural investigations also will includes transmission electron microscopy investigation that will give direct information about quality of the InGaAsN-GaN HSs and allow features of the self-organized processes in this system to be understand. Optical investigations (PL, absorption, reflectance) will give information about value of the band gap, impurity presence, quality of the structures. Transport measurements is useful tool for characterization of the electrical properties of the InGaAsN layers and (Al,Ga)N:As alloys (carrier concentration, mobility). Combination of the structural, optical and transport measurements and comparison of these results with growth details allow the technology of high quality InGaAsN layers and HSs to be developed.
Theory
Work on growth and investigations of the properties of InGaAsN-GaN system will be accompanied by theoretical studies. This theory will include investigations of self-organized processes and optical properties connected with inhomogeneity and domain structure of InGaAsN-GaN HSs. Study of the field interaction with domain structures is based on scattering properties of a single domain. Scattering at single domain will be investigated in long-wave approximation. Periodic domain structures will be analyzed with the help of spatial averaging over infinitely small volume and effective constitutive parameters of semiconductor domain ensemble in long-wave approximation will be found. It permits to consider optical properties of nanoscale domain HSs. Study of charge carrier transport is also supposed with the help of semiclassical transport model, as well as effective medium approach and MAB (Minimum Autonomic Block) method including kinetic phenomena.
Post-growth processing and device fabrication
Post-growth processing via annealing at different temperatures give it possible to improve characteristics of the structures. Dependence of the electrical, optical and structural properties of the InGaAsN layers and HSs on annealing conditions will be investigated.
Device fabrication will start after development of the technology of fabrication of the high quality InGaAsN layers and HSs and investigations their basic properties. This will includes fabrication of the contact layers on basis of the results of the influence of As concentration on the electrical properties of AlGaN. Investigations of the optical properties of the InGaAsN-GaN system will permit active region of the LEDs to be designed. Spectral, threshold and output power characterization of the LEDs will be carried out. Influence of different post-growth processing on the device parameters will be investigated.
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