Layered Transition Metal Dichalcogenides in Cutting-Edge Optoelectronic and Synaptic Technologies

Two-dimensional (2D) transition metal dichalcogenides (TMDs), with their unique properties, have drawn remarkable attention for fundamental research as well as for investigation on technological breakthroughs in various applications, viz. photonics and optoelectronics, neuromorphic computing, spintronics, quantum computing, quantum emitters, and detectors, etc. In this talk, I will discuss different pathways to realize 2D TMD-based hybrid transistors with superior performance for photodetection and synaptic applications. Fabrication of high-performance phototransistors demands superior channel material, which should be of high carrier mobility for high gain bandwidth product, a direct bandgap for efficient optical absorption, a thinner layer for full depletion leading to ultralow dark current, and very low trap state density for low subthreshold swings. Layered semiconducting 2D TMDs fulfill most of these requirements; however, they suffer from a trade-off in device performance due to the simultaneous occurrence of both absorption and amplification processes within the single-semiconductor channel layer. To address this issue, I will discuss the advantages of mixed-dimensional photo field effect transistor architecture by integrating strongly light-absorbing semiconducting nanocrystals with the 2D channel layer having superior charge transport properties to get high responsivity as well as broad spectral response in a photodetector. I will also discuss the benefits of asymmetric metal contacts as source and drain electrodes for achieving very low dark current values (~ pA) without applying any gate bias, making them promising for high-sensitive detector fabrication [1]. Further, I will discuss the opportunities of 2D material-based mixed-dimensional architecture to fabricate optoelectronic synaptic devices that can detect, process as well as store optical signals in the same device, enabling faster, more efficient, and highly parallel information processing in the “big-data” era. Analogous to the biological synapses, these devices reveal short-term plasticity behavior like excitatory postsynaptic current and paired pulsed facilitation, and also the revolution from short-term plasticity to long-term plasticity, making them an excellent prototype for artificial intelligence vision systems [2].

References:

1. S. Das, A. Ghorai, S. Pal, S. Mahato, S. Das, and S. K. Ray, "Photosensitive Field-Effect Transistor with Enhanced Photoamplification Mediated by Charge Transfer in a Heterostructure of α- CsPbI3 Nanocrystals and Two-Dimensional WS2," Phys. Rev. Appl. 19(3), 034051 (2023).

2. S. Das, V. Pal, S. Mukherjee, S. Das, C. S. Tiwary, and S. K. Ray, "MultiWavelength Optoelectronic Synaptic Transistors Based on Transition Metal TellurideSulfide Heterostructures," Adv. Opt. Mater. (2024)