Bipolar Photoresponse of a Graphene Field-Effect Transistor Induced by Photochemical Reactions

Abstract

Graphene is an air-friendly material that can be easily p-doped by oxygen; therefore, a stable, defect-free, and efficient graphene n-doping technique should be developed for achieving high performance in electronic and optoelectronic devices. In this study, we present a unique method for n-type chemical doping of monolayer graphene grown through chemical vapor deposition. The doping process is thoroughly examined using X-ray photoelectron spectroscopy, Raman spectroscopy, and ultraviolet photoelectron spectroscopy. The findings demonstrate that the use of KBr solution is highly effective in achieving n-type doping in monolayer graphene, offering promising prospects for its practical application. Also, we fabricated graphene field-effect transistors and studied their electrical properties before (pristine) and after doping the graphene channel with different KBr concentrations (0, 0.05, 0.15, 0.20, and 0.25 M) in dark and under deep-ultraviolet (DUV) light conditions. During graphene doping in the dark environment, the charge neutrality point (CNP) shifted toward negative back gate voltages and then saturated at 0.25 M. After photochemical doping under DUV light, CNP further shifted toward negative gate voltages with improved carrier mobility at the same molar concentration of 0.25 M. Additionally, the photodetectors are fabricated from pristine and doped graphene which demonstrated bipolar photoresponse, thereby, a transition of negative photocurrent to a positive photocurrent when the concentration of the KBr solution reached 0.20 M. Moreover, their response time decreased from 8 to 3.5 s with increasing KBr concentration from 0 to 0.30 M. Finally, the gate voltage-dependent broadband photoresponsivity of doped graphene (0.25 M) was investigated at different wavelengths (220, 365, 530, and 850 nm). Thus, the controlled doping-induced bidirectional photoresponse can provide a facile route for logic gate applications.

Gate-tunable rectification and photoresponse in a MoTe2/SnS2 van der Waals heterostructure based P–N diode

“…This behavior is related to strong absorption and high photon energies at low wavelengths, which is compatible with the findings of earlier research. 54 We have calculated the responsivity ( R ) and external quantum efficiency (EQE) at various wavelengths of incident light. The values of R and EQE decreased as the wavelength of incident light was enhanced as shown in Fig.…”

Recent Advances in the Raman Investigation of Structural and Optical Properties of Graphene and Other Two-Dimensional Materials

“…By identifying the doping levels, Raman spectroscopy enables the fine-tuning of the electronic properties of these transistors, directly affecting their speed and energy efficiency. Additionally, the technique provides valuable data on heat generation and dissipation within the FETs, contributing to their long-term stability and performance [92][93][94][95].…”

Contemporary innovations in two-dimensional transition metal dichalcogenide-based P–N junctions for optoelectronics

“…1–6 2D materials have established a significant deal of devotion in the fields of spintronics, 7–12 electronics, 13–17 and optoelectronics. 15,18–24 Scientists were sure that heat fluctuation made it difficult for nanoparticles to maintain stability, which ultimately caused a breakdown. The thermally stable graphene in this scenario has greatly surprised scientists, spurring the rapid growth of the 2D materials research field over the past few decades.…”