Project funded by the National Science Centre under the “Preludium 19” call
Project number: 2020/37/N/ST3/0224
Total project value: 196,800.00 PLN
Total funding: 196,800.00 PLN
Project implementation period: 05/17/2021 – 05/16/2024
Project leader: Dr. Dominika Majchrzak
AlGaN is characterized by a wide, direct bandgap in the UV range (from 3.4 eV for GaN to 6.2 eV for AlN), which makes it an excellent candidate for deep-UV LED structures. Deep-UV emitters can be used in sterilization, water or air purification, and as UV sensors. For sterilization and disinfection, the best performance is achieved with LEDs emitting at wavelengths below 280 nm, which are highly effective at eliminating bacteria and viruses.
Mercury lamps currently dominate the UV-emitter market. LEDs based on AlGaN offer many advantages compared to mercury lamps, including low toxicity, tunability of the emission wavelength, compact size, long operational lifetime, no warm-up time, and low operating voltage. Their only drawback is the low emission efficiency of such devices.
The scientific objective of this project is to improve the electrical properties of Al-rich p-type AlGaN layers using a specially designed gradient AlGaN:Mg contact layer. The project focuses on enhancing electrical parameters such as hole concentration and sample resistivity by optimizing the thickness of the gradient AlGaN:Mg layer, as well as the structural properties of the entire grown structure.
The hypothesis of this project is that an optimized gradient AlGaN contact layer will improve the ohmic behavior of high-Al-content (~60%) AlGaN:Mg layers. It is also expected that the specific contact resistivity will decrease with increasing thickness of the gradient AlGaN layer (up to a certain critical thickness, beyond which defects introduced into the structure may deteriorate electrical properties).
Within this project, such samples will be systematically grown for the first time using two different epitaxial methods: metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). The electrical properties of the grown structures will be examined, including Hall-effect measurements.
The obtained results will be compared with theoretical simulations of energy bands and charge-density profiles as a function of depth, enabling a deeper understanding of the physical phenomena occurring in such structures. It is expected that the successful implementation of this innovative approach will help overcome one of the key factors limiting emission efficiency (low hole concentration in the p-AlGaN layer) of semiconductor deep-UV emitters, thus increasing their application potential relative to mercury lamps.
Because such devices may find use in numerous areas of everyday life, we are fully convinced that the research proposed in this project will significantly contribute to the advancement of science, technology, and society.
