CMOS/GaN integration in micro/nanoLED arrays for biomedical applications

Abstract

[eng] Since their inception, LEDs have replaced traditional incandescent and fluorescent lighting in numerous sectors, ranging from general illumination and display technologies to specialized applications, such as in the biomedical field. LEDs provide significant energy savings, reduced environmental impact, and greater design flexibility, marking a significant shift in how light is utilized across different domains, even being able to substitute lasers in a wide range of applications. Building on the success of conventional LEDs, microLED technology has emerged as a groundbreaking advancement. MicroLEDs are significantly smaller than traditional LEDs, typically ranging from a few micrometers to a few hundred micrometers in size. This miniaturization opens new possibilities for high-resolution displays, where microLEDs offer superior brightness, contrast, and energy efficiency compared to OLED and LCD technologies. Additionally, the fast response times and robustness of microLEDs make them suitable for dynamic and demanding applications, such as augmented reality and virtual reality displays, as well as advanced biomedical devices. The integration of CMOS technology with GaN microLEDs in the development of products based on micro or nanoLED arrays is a significant step forward for all the applications where microLEDs can be used. In this work, we will focus on their potential usage in the biomedical field. CMOS technology is known for its scalability, low power consumption and high integration density, which are essential characteristics for creating compact and efficient electronic systems. On the other hand, GaN is valued for its high electron mobility, thermal stability and direct wide bandgap properties, enabling efficient light emission and operation under high power conditions. Combining these technologies, it is possible to create lighting devices with micro or nanoLEDs that leverage the best attributes of both materials, resulting in a compact device with enhanced performance and functionality. This PhD thesis explores the development of CMOS drivers to be integrated with GaN microLED arrays, addressing the inherent challenges posed by the material and processing incompatibilities between silicon-based CMOS and GaN. This research provides a detailed analysis of the optical, electrical, and thermal performance of these devices, demonstrating their superior characteristics compared to conventional LED arrays and other light sources. In the context of biomedical applications, the thesis focuses on microscopy and PoC diagnostics. In advanced microscopy, integrated micro/nano LED arrays can provide high-intensity, uniform illumination with precise control over wavelength and intensity. This capability enhances imaging resolution and contrast, allowing for more detailed and accurate observations at the cellular and molecular levels. The miniaturized form factor of these LEDs also facilitates the development of compact and portable microscopy devices, broadening their accessibility and utility in various medical and research settings. Furthermore, in this thesis we explore the use of micro and nanoLED devices combined with CMOS electronics to create a new type of microscopy technique, Nano-Illumination Microscopy (NIM). For PoC diagnostics, the high speed and high optical power that microLEDs can deliver when driven by CMOS IC is crucial to develop fluorescence based PoC. These arrays can be used to develop portable diagnostic devices that offer real-time monitoring and rapid analysis of biological markers. This is crucial for early disease detection and personalized medicine, where timely and accurate diagnostics can significantly improve patient outcomes. The integration of these LEDs into PoC devices ensures that they are not only effective but also energy-efficient and cost-effective, making them suitable for widespread use, including in resource-limited settings. Furthermore, microLED arrays are a perfect fit to accomplish the ASSURED criteria provided by WHO for PoC devices. In conclusion, this PhD thesis shows that the integration of CMOS and GaN technologies in micro/nano LED arrays offers a transformative approach for advancing biomedical applications, specifically in microscopy and PoC diagnostics. The enhanced performance, combined with the reliability and scalability of these integrated systems, holds significant promise for future innovations in medical diagnostics, treatment, and research. This work lays the groundwork for further exploration and development in the field, potentially leading to new breakthroughs in biomedical technology.

[spa] Desde su aparición, los LEDs han reemplazado a las luces incandescentes y fluorescentes en muchos sectores, desde la iluminación general y las tecnologías de pantallas hasta aplicaciones especializadas, como en el campo biomédico. Los LEDs ofrecen un considerable ahorro energético, menor impacto ambiental y mayor flexibilidad de diseño, cambiando la manera en que se utiliza la luz en distintos dominios, incluso como sustitutos de los láseres en diversas aplicaciones. A partir del éxito de los LEDs convencionales, la tecnología microLED ha surgido como un avance revolucionario. Los microLEDs son mucho más pequeños, con tamaños que van desde unos pocos micrómetros hasta cientos de micrómetros. Esta miniaturización permite nuevas posibilidades para pantallas de alta resolución, donde ofrecen mayor brillo, contraste y eficiencia energética que las tecnologías OLED y LCD. Su rápida respuesta y robustez los hacen ideales para aplicaciones como la realidad aumentada y virtual, así como en dispositivos biomédicos avanzados. La integración de la tecnología CMOS con microLEDs de GaN en el desarrollo de productos basados en matrices de micro o nanoLEDs es un paso adelante para todas las aplicaciones en las que se utilizan. Esta tesis doctoral se centra en su uso potencial en el campo biomédico. La tecnología CMOS es valorada por su escalabilidad y bajo consumo energético, mientras que el GaN se destaca por su alta movilidad electrónica y estabilidad térmica. Combinando estas tecnologías, se pueden crear dispositivos compactos con micro/nanoLEDs que ofrecen un rendimiento mejorado. Este trabajo explora el desarrollo de controladores CMOS integrados con matrices de microLED de GaN, analizando su rendimiento óptico, eléctrico y térmico. En el ámbito biomédico, se destaca su aplicación en microscopía avanzada y diagnósticos en el punto de atención (PoC). En microscopía, los micro/nanoLEDs integrados ofrecen iluminación de alta intensidad con control preciso, mejorando la resolución de las imágenes. Además, gracias a estos dispositivos, se ha podido crear un nuevo tipo de microscopios, los microscopios de barrido. En diagnósticos PoC, su alta velocidad y potencia óptica permiten el desarrollo de dispositivos portátiles y eficientes para la detección temprana de enfermedades. En resumen, esta tesis muestra que la integración de CMOS y GaN en micro/nanoLEDs tiene un gran potencial para avanzar en las aplicaciones biomédicas.