| Title: | Struktury kwantowe o bardzo szerokim spektrum emisji i zwiększonej intensywności emisji dla nowej generacji diod superluminescencyjnych InGaN/GaN |
| Project leader: | Grzegorz Staszczak |
| Laboratory: | Laboratory of Semiconductor Characterization (NL-12) |
| Call/Programme name: | OPUS |
| Project number: | 2021/41/B/ST7/04145 |
| Implementation date: | 21.01.2022 20.01.2025 |
| Implementing entity: | Instytut Wysokich Ciśnień Polskiej Akademii Nauk |
| Total funding granted: | 1 417 032 zł |
| Funding for the entity: | 1 417 032 zł |
| Funding institution: | National Science Center |
Project description
| Aim of the project is to develop a technology for the fabrication of new generation of superluminescent diodes (SLD) with a wide spectrum of light (>25 nm) operating in the visible light range (400-440 nm). Nitride semiconductor based light emitters are widely used in our daily life. The popular are light emitting diodes (LED) and laser diodes (LD). This family of emitters also includes the lesser known SLD, combining the spatial coherence of the emitted light typical for LDs with the low time coherence (wide emission spectrum) typical for LEDs. Due to these specific properties, SLDs are perfect, first of all, in fiber optic gyroscope (FOG) and in medical imaging systems, like optical coherence tomography (OCT), where low time coherence and high quality of the light beam are required. In SLDs, the main problem is to obtain a sufficiently wide emission spectrum and high output power. Several methods have been proposed to broaden the nitride SLDs spectrum. Unfortunately, they do not bring the expected results - spectrum widening takes place at the cost of a significant drop in optical power due to the high built-in electric field, the presence of nonradiative centers, problems with high indium concentration, etc. In order to solve these problems, we propose the use of an innovative structure of SLD active area consisting of a set InGaN/GaN qunatum wells, QWs (type I) or a set of InGaN/GaN short period superlattices, SLs (type II), with various geometries extremely narrow QWs of 0.5–2 nm, variable indium content, x≤0.25, and different QBs width 0.75-6 nm within each structure type. By selecting the widths of QWs and/or QBs, we will be able to obtain simultaneous emission at several wavelengths (from individual QWs or SLs), which will translate into a wider spectrum of light. In SLs the wave functions of the QWs and the QBs interact, and thus modification of their properties (including optical properties) is possible. Project implementation consists in performing the following tasks: • Simulations of the LED test structures with different geometries; optimization of their optoelectronic properties (WP1); • Preparation of LED test structures of type I (WP2) and II (WP3) with different geometries. Optimization of the growth conditions (optical, structural, and electrical characterization); • Fabrication of SLDs of types I and II. Processing of the SLD chips and optimizing the design of the waveguides and the entire resonant cavity(WP4). Quantum structures investigated in this project will be grown by metalorganic chemical vapour deposition (MOCVD) technique. LED test samples will be grown on sapphire, while SLDs will be grown on high quality GaN substrates. Structural studies will be carried out on transmission electron microscopy (TEM), X-ray diffractometer (XRD) and atomic force microscopy (AFM). The optical properties (emission energies and spectral width, built-in electric fields, piezoelectric effects) of the samples will be investigated by cathodoluminescence and photoluminescence measurements at various temperatures, excitation laser powers and hydrostatic pressures. The electric properties of the SLDs will be examined by measuring the L-I (optical power vs current) and U-I (voltage vs current) characteristics. Theoretical studies of the investigated structures will also be carried out. Electronic and optical properties will be calculated using the ab-initio method and simulated using commercial software. Nitride SLDs represent still an innovative type of emitters. There are not many studies on the use of nitrides in SLDs and this field is still very underdeveloped. On the other hand, the use of materials based on nitrides allows to obtain emissions in very wide spectrum (from UV to red). This means that SLDs based on these materials offer new possibilities of applications, previously unavailable for other material systems. The innovative approach proposed in the project, consisting in the use of modified structures of the active area, aims to meet the conditions required in SLD applications. Obtaining simultaneous emission at different wavelengths (wide emission spectrum) will result in showing "proof of concept" regarding in particular the applicability of short period SLs in the new generation of SLDs. This knowledge will represent a new and significant contribution to the state of the art in the field of light emitters and could also contribute to the field of basic research in semiconductor based optoelectronics. |