Two-dimensional (2D) semiconductor materials, featuring atomically thin structures and high tunability, offer opportunities for transcending the limitations of traditional semiconductor materials such as short-channel effect and surface defects, thereby extending Moore’s law and further enhancing chip integration density, positioning themselves as the next-generation electronic materials in the post-Moore era [
1]. However, the pronounced interlayer electron concentration of 2D-material, influenced by surface effects and lattice characteristics, typically manifests in n-type or predominantly n-type bipolar semiconductor behavior. This circumstance emphasizes the urgent necessity for exploring complementary p-type low-dimensional semiconductor materials in constructing field-effect transistors (FETs), complementary metal-oxide semiconductors (CMOSs), and various optoelectronic devices [
2]. Moreover, due to surface phonon scattering arising from lattice defects, the carrier mobility of two-dimensional semiconductor materials is relatively insufficient, considerably inferior to that of silicon (Si), thus the exploration of p-type 2D semiconductors with high hole mobility is crucial for low-dimensional electronics [
3]. Among a variety of 2D materials, black phosphorus (BP) demonstrates p-type-dominated bipolar characteristics with an impressive hole mobility of up to 1000 cm
2/(V·s) at room temperature. Nevertheless, the high chemical reactivity of BP, attributed to lone-pair electrons on its surface and edges, results in rapid degradation in the presence of atmospheric water and oxygen, thereby limiting its compatibility with conventional semiconductor integration processes and hindering its long-term stability [
4]. Therefore, the quest for p-type two-dimensional semiconductors that exhibit both stability in ambient air and high mobility holds significant research value in the study of 2D semiconductor materials in the post-Moore era.
Tellurium (Te), as a chalcogen-element semiconductor, exhibits an exceptional anisotropic trigonal crystal structure composed of van der Waals-bonded molecular chains, which enables Te to stably exist in both one-dimensional (1D) and two-dimensional (2D) forms [
5]. Similar to graphene and black phosphorus (BP), the distinctive structural and elemental features entitle low-dimensional Te to possess not only the characteristic van der Waals structure, such as the absence of dangling bonds, atomic-scale thickness, and exceptional mechanical properties, but also the advantages of elemental semiconductors, including a simple and stable composition, high tunability, and intrinsic material benefits. Remarkably, 2D Te as a P-type semiconductor, not only possesses superior hole mobility [1370 cm
2/(V·s)] [
6] but also exhibits exceptional chemical stability, along with its thickness-dependent bandgap ranging from 0.31 eV in bulk to 1.04 eV in the monolayer [
7]. The anisotropic crystal structure of Te imparts polarization-dependent optoelectronic properties [
8], coupling with the exceptional durability, mobility, and p-type characteristics, positioning 2D Te as a pivotal material system for constructing high-performance, reliable 2D material-based electronic and optoelectronic devices [
9,
10].
The extraordinary and rare advantages of 2D Te have elevated it to the forefront of contemporary research, and a recent comprehensive review [
Front. Phys. (Beijing) 18(3), 33601 (2023)] [
4] has elucidated the profound significance of 2D-Te, systematically detailed its unique structural attributes and preparation methodologies, and emphasized its forefront applications in next-generation electronics and optoelectronics. Specifically, the review thoroughly introduced the preparation methodologies of 2D-Te such as hydrothermal method, liquid-phase exfoliation, chemical vapor deposition, and physical vapor deposition, and each effort to achieve precise control over morphology, thickness, and crystalline quality. In terms of applications, the review focused on Te-based devices, including field-effect transistors (FETs), broadband photodetectors, and van der Waals heterostructure photodiodes, concluding their latest achievements in performance. For instance, Te-based FETs have demonstrated hole mobilities as high as 1370 cm
2/(V·s) when fabricated on h-BN substrates, surpassing most conventional 2D materials, and the photodetectors based on Te show an ultra-wide photo response range from visible to mid-infrared (500−2500 nm), achieving specific detectivities up to 1.23 × 10
12 Jones. Additionally, Te incorporated into van der Waals heterostructures enables high-performance, self-powered photodetectors with remarkable polarization sensitivity and photocurrent switching ratios exceeding 10
5, paving the way for advanced polarization-sensitive imaging and infrared detection technologies. The review addressed emerging challenges and opportunities in advancing Te-based technologies, including the need for controlled synthesis techniques and optimization strategies to fully harness its unique properties. Over these accomplishments, the review further emphasized emerging challenges and opportunities in advancing Te-based technologies including the advancement of controlled synthesis techniques and optimization strategies to fully harness its unique properties.
Beyond wide applications in electronic and optoelectronics, 2D semiconductors have been recognized as ideal platforms for constructing topological quantum devices with unique nontrivial band structures and carrier transport properties, owing to their unique crystalline structures and exceptional tunability. However, current research on Weyl fermions and Weyl physics has been primarily confined to semimetal systems, while topological Weyl semiconductors with novel topological properties and semiconductor characteristics, which are considered more significant from device-constructing perspective, remain unexplored. Additionally, a variety of low-dimensional material systems usually rely on external field modulation to induce topological phase transitions, such as electric fields, magnetic fields, strain, or pressure. Thus, discovering materials that inherently possess both topological properties and semiconductor characteristics is crucial for advancing the development of next-generation quantum devices.
The intrinsic chiral helical crystal structure of Te lacks spatial inversion symmetry but retains rotational symmetry, resulting in robust spin−orbit coupling and symmetry-protected Weyl points within its band structure, which enable Te to exhibit intrinsic topological properties without requiring external modulation. Te has been reported to possess intriguing transport phenomena as negative longitudinal magnetoresistance (NLMR) [
11], planar Hall effect (PHE) [
12], and circular photogalvanic effect (CPGE) [
13], whose magnetoresistance and Hall data show logarithmically periodic oscillations beyond the quantum limit indicative of discrete scale invariance (DSI) [
12], providing strong evidence for the presence of Weyl fermions in Te. Different from conventional topological semimetals, the Weyl points of Te are located at the top valence band, approximately −0.20 eV below the Fermi level, which is also the origin of its Berry curvature, giving it a unique combination of nontrivial topological properties and semiconductor bandgap characteristics. This dual nature defines Te as a “topological semiconductor” representing a groundbreaking class of topological materials that provides a foundational scientific model for exploring the existence and tunability of topological states in semiconductors [
12], which significantly advances the integration of topological physics with traditional semiconductor technologies. Recently, room-temperature non-linear Hall effect (NLHE) induced by topological feature has been observed in Te, and its semiconductor feature makes it uniquely tunable by gate bias [
14,
15]. This tunability further realizes a dissipationless Hall response in NLHE [
16], providing a potential application in pyroelectric detectors, proving the significance of the topological semiconductor. Similarly, the semiconductor feature entitles the gate bias to tune the Fermi level from the top of the valence bands into the bandgap, departing from Weyl nodes, which induces the capability of suppressing the chirality-related topological transport and eliminating NLMR [
17]. Therefore, Te as a pioneering topological semiconductor, paves avenues for the development of next-generation quantum devices that seamlessly integrate topological states with traditional semiconductor functionalities, offering a promising platform for innovative applications in future quantum technology.
In conclusion, the unique combination of high hole mobility, stability, and topological properties makes Te a promising material for a wide range of applications, from FET to quantum devices, as illustrated in Fig.1. Recently, besides its outstanding semiconductor and topological characteristics, Te has also made notable advancements in thermoelectric [
21], memristor [
22], strain engineering [
23], and so on. As research progresses, overcoming challenges in synthesis and integration will be essential for the actual application of Te, which is poised to play a pivotal role in low-dimensional material systems, offering exciting possibilities for the future of electronics, optoelectronics, and beyond.