Electrical and Optoelectronic Properties of Two-Dimensional Lateral Heterostructure Semiconductors
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Nanotechnology (MPNAT), MSc
Publicerad
2024
Författare
Krishna Kumar, Baskar
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Two-Dimensional (2D) semiconductors are promising materials for atomically thin
electronics and optoelectronics. Specifically, p-n junctions and their gate voltagecontrolled effects in the lateral heterostructures of such 2D semiconductors offer
several advantages because of their atomically thin in-plane superlattices. 2D p-n junctions have great potential for application in low-power, high-performance
electro-optical devices, such as tunnel transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although vertical heterojunctions are promising for
electro-optical devices, the use of mechanical exfoliation process to obtain the vertical heterostructure is unsuitable for wafer-scale fabrication. The in-situ growth of
high-quality lateral heterostructures with multiple junctions has just started to be
explored.
In this master’s thesis, we fabricated field-effect transistors (FETs) based on MoS2-
WS2 lateral heterostructures and performed their electrical and optoelectronic characterization. The lateral heterostructures grown using the water-assisted one-pot
chemical vapour deposition (CVD) are used to fabricate the back-gated FETs on
Si-SiO2 substrates with Ti/Au contacts. We characterized the individual MoS2
and WS2 channels and their heterojunctions. The junctions show diodic behaviour,
which could be understood by the formation of n-n+ junction. The transistor parameters are extracted for MoS2, WS2 and MoS2-WS2 heterojunction. Furthermore,
we observed a persistent photoconductivity (PPC) effect with a time constant of 10
hrs at the heterojunction. The PPC effect is being explored for applications such as
optoelectronic synapses, optical memory, artificial vision etc.
Beskrivning
Ämne/nyckelord
Two-dimensional semiconductors MoS2-WS2 lateral heterostructure, backgated field effect transistors, persistent photoconductivity effect