Photo-induced doping in hexagonal Boron Nitride: Towards new UVC LED structure. – BIRD

Often considered as detrimental, defects in semiconductors such as vacancies or impurities can reduce drastically the performances of optoelectronic devices. Defects can also be functionalized to provide new properties to semiconductors. Layered 2D materials known for their exceptional properties such as ability to form Van der Waals heterostructure, or bandgap tuning by changing the number of layers, are also gaining interest due to the properties of their defects. More precisely, also linked to defect centers, persistent photoconductivity (PPC), a phenomenon in which photo-induced conductivity persists after turning off the illumination, has been observed to last for days at room temperature in some 2D materials. IRL GT-CNRS recently evidenced for the first time that 2D h-BN exhibits significant PPC at room temperature for many years after sub bandgap UV illumination clearly indicating that after UV exposure, h-BN can be durably converted from insulator to conductor. These new observations could path the way toward h-BN usage for optoelectronics and especially deep UV emission.
BIRD project’s goals are thus to:
• Reveal the underlying mechanism of insulator to conductor transition in 2D layered h-BN after deep UV illumination. The exact reason for giant PPC in h-BN is indeed still unknown hindering the development of the photoinduced doping effect. As such, identification of the defects responsible for PPC will be a fundamental input to favor their formation during metal organic chemical vapor deposition growth.
• Optimize the giant PPC effect and effectively use it as a novel doping method. Understanding the physics behind the giant PPC effect in h-BN is a first requirement for that.
• Demonstrate its proper usage we aim toward the realization of h-BN homojunctions using the photoinduced doping process to produce conductive h-BN layers. Integrating BAlN/BN quantum wells would then be the next step toward highly efficient DUV LEDs