Two-Dimensional Material-Based Quantum Dots for Wavelength-Selective, Tunable, and Broadband Photodetector Devices

Abstract

The rise of atomically thin two-dimensional (2D) materials brings a revolution in material science and engineering, and encouraged worldwide scientists to integrate desired 2D materials into electrical circuitry by non-covalent interactions. Regardless of some unique properties including super-flexibility, broadband absorption and high carrier mobility, the weak optical absorption due to the thinness of 2D layers restricts their commercial use for photodetection. On contrary, quantum dot (QD) of 2D materials can overcome the weak absorption problem due to the strong quantum confinement, high absorption coefficient combined with the superlative features and properties of 2D layers. Therefore, 2D QDs have become a powerful contender for next-generation photodetection technology. Moreover, bandgap engineering by controlling the QD size due to strong quantum confinement and further integration with other materials are the most adaptable strategy to design high-performance, wavelength-tunable multicolour photodetector devices. It should be noted that the optical sensing for the infrared spectral region is of paramount importance in recent years, for many applications, especially environmental monitoring, security camera, military application, etc., but such applications in 2D-based QDs are limited. Alternatively, QD-based photodetector fabrication strategies such as epitaxial growth, heterostructure integration, functionalization and colloidal synthesis became mature from a material science perspective to achieve a broad spectral tunability. This chapter provides a comprehensive summary over the latest scientific and technological progress of QD-based photodetectors fabricated for the ultraviolet to infrared regime using van der Waals (vdW) materials, focusing mainly on carbon-based QDs, transition metal dichalcogenides (TMDCs) and black phosphorus (BP) QDs. We first start with the structural and optical properties of various 2D QDs. Secondly, the several strategies to synthesize 2D QDs and the different state-of-the-art device fabrication technology to improve the device performance have been described by addressing the inherent critical challenges. Thereafter, a brief but essential survey of emerging 2D QDs and their on-chip integration with other semiconductors in heterostructure form for photodetection application have been discussed. Finally, the chapter summarizes the comparison of performance of several 2D QD-based photodetectors highlighting the underlying challenges and opportunities for the future development of vdW QD-based research to realize their industrial scale-up.