Se-Vacancy Healing with Substitutional Oxygen in WSe₂ for High-Mobility p-Type Field-Effect Transistors

Abstract

Transition-metal dichalcogenides possess high carrier mobility and can be scaled to sub-nanometer dimensions, making them viable alternative to Si electronics. WSe2 is capable of hole and electron carrier transport, making it a key component in CMOS logic circuits. However, since the p-type electrical performance of the WSe2-field effect transistor (FET) is still limited, various approaches are being investigated to circumvent this issue. Here, we formed a heterostructural multilayer WSe2 channel and solution-processed aluminum-doped zinc oxide (AZO) for compositional modification of WSe2 to obtain a device with excellent electrical properties. Supplying oxygen anions from AZO to the WSe2 channel eliminated subgap states through Se-deficiency healing, resulting in improved transport capacity. Se vacancies are known to cause mobility degradation due to scattering, which is mitigated through ionic compensation. Consequently, the hole mobility can reach high values, with a maximum of approximately 100 cm2/V s. Further, the transport behavior of the oxygen-doped WSe2-FET is systematically analyzed using density functional theory simulations and photoexcited charge collection spectroscopy measurements.

Solution-Processable and Printable Two-Dimensional Transition Metal Dichalcogenide Inks

“…Metal chlorides, such as SnCl 4 , FeCl 3 , and AuCl 3 , have also been explored as chemical dopants for p -type TMD flakes . Another strategy is to use oxygen doping from inorganic aluminum-doped zinc oxide to the WSe 2 channel that can heal Se deficiency and achieve high-mobility p -type FETs . But the chemical doping approaches are facing challenges in material and performance robustness at an elevated temperature (e.g., >100–200 °C) or continual electrical bias due to the relatively unstable molecular doping.…”

Chalcogen Vacancy Engineering of Two-Dimensional Transition Metal Dichalcogenides for Electronic Applications

“…(f) Comparison of μ h and on–off ratio for pristine and O-doped WSe 2 transistors. Reproduced with permission from ref . Copyright 2023 American Chemical Society.…”

“…The electronic properties of WSe 2 -based FETs can be improved by reducing the SeVs through aluminum zinc oxide (AZO) treatment . The AZO treatment process, which is performed in solution, includes the following steps: spin-coating on WSe 2 FETs, annealing, and wet etching (Figure e).…”

High-Photosensitivity WSe2 Phototransistor with Electrically Self-Isolated C8-BTBT as a Light Absorption Layer

“…Recently, two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS 2 , MoSe 2 , WS 2 , and WSe 2 , have attracted tremendous attention as next-generation semiconductors due to their fascinating electrical and optical properties. − The electrical properties of 2D TMD-based field effect transistors can be effectively and nondestructively tuned by coating various organic molecules on their surface due to surface charge-transfer doping or formation of heterostructures. − However, many previous reports found that this may result in an increase of both ON and OFF current, severely limiting the signal-to-noise ratio (SNR) when applied to photosensing applications (i.e., phototransistors). − An example of such an increase in OFF current after coating organic molecules on a 2D TMD-based transistor is shown in Figure S1. Therefore, the effective application of organic coatings on TMD-based phototransistors dictates that it is necessary to limit potential OFF current increases and act as a light absorption layer to improve the photosensitivity (i.e., SNR) of TMD-based phototransistors.…”