Benefiting from intriguing and unique physical properties such as narrow bandgap and high mobility, antimonides have been considered promising building blocks for next-generation, high-performance infrared photodetectors, and high-speed integrated circuits. As typical low-dimensional structures, nanowires (NWs) possess superior crystal orientation and a high surface-to-volume ratio, rendering antimonide NWs highly sensitive to external variables. These attributes position antimonide NWs as promising candidates for the next generation of electronic and photoelectronic nanodevices. Simultaneously, the development of Gate-All-Around FETs based on small-diameter NWs is considered an effective approach for realizing the new generation of optoelectronic logic devices.

Due to the outstanding surface area, a significant number of suspended bonds exist on the surface of antimonide NWs, resulting in pronounced surface states. Typically, these surface states induce a severe surface Fermi level pinning effect and deteriorate the performance of optoelectronic devices, which seriously limits the application of antimonide NWs in high-performance electrical and optoelectronic devices. In response to this, Prof. Yang Zaixing's group from the School of Physics conducted a series of surface engineering techniques to control the suspended bonds on the surface of antimonide NWs. Consequently, they successfully mitigated the surface states, overcame the surface Fermi level pinning effect, and achieved the anticipated high-performance optoelectronic device.

Process 1. Control the suspended bonds on the surface of antimonide NWs by adopting an amorphous chalcogenide semiconductor as a passivation shell.

The construction of a core-shell heterostructure proves to be an effective strategy for passivating the surface states of antimonide NWs. However, the lattice mismatch issue at the radial interface challenges the construction of core-shell heterostructure NWs. In prior work, the "skin effect" of antimony was effectively suppressed by utilizing chalcogenide elements as surfactants (Nature Communications 2014, 5, 5249). This approach yielded antimony NWs with a uniform distribution and controllable diameter. Recently, Yang Zaixing's group achieved successful growth of an amorphous chalcogenide semiconductor as a passivation shell, leveraging chalcogenide elements as "bonds". Adopting amorphous chalcogenide semiconductor passivation shells resolves the lattice mismatch issue at the radial interface during the construction of core-shell heterostructure NWs. The composition, diameter, shell thickness, and surface morphology of the as-constructed core-shell NWs are well controlled. After the successful construction of core-shell heterostructure NWs, the surface states of antimonide NWs are effectively regulated the stability is significantly improved. Additionally, the as-constructed core-shell NWs demonstrate intriguing photodetection performance. Specifically, the GaSb/GeS core-shell NW exhibits the type-I heterostructure with distinctive wavelength-dependent bi-directional photoresponse behavior and excellent visible light-assisted infrared photodetection performance. Notably, this developed strategy proves to be an efficient and versatile approach for the lattice-mismatch-free construction of core-shell heterostructure NWs. This methodology has been validated across various NWs, including GaAs/GeS, InGaAs/GeS, and CdS/GeS core-shell heterostructure NWs.This work entitled "Lattice-mismatch-free construction of III-V/chalcogenide core-shell heterostructure nanowires" has been published in Nature Communications (2023, 14, 7480).

Fig. 1 Lattice-mismatch-free construction of core-shell heterostructure NWs and the photodetection performance of as-constructed GaSb/GeS core-shell heterostructure NWs.

Process 2. Inhibit the charge-trapping effect of the surface states by growing Al₂O₃as shell with a low-temperature solution-annealing method.

The surface states of antimonide NWs consistently act as charge traps, introducing bias-stress instability and hindering their potential application in next-generation optoelectronic devices. Effectively addressing these surface states is crucial for optimizing the performance of optoelectronic devices. Yang et al., mitigate the charge-trapping effect of surface states by employing a low-temperature solution-annealing method to grow AlOx as shells. This method is characterized by its simplicity, cost-effectiveness, and compatibility with existing CMOS technology. Benefiting from the unique electric double layer in the AlOxshell, the surface charge traps of antimonide NWs are successfully suppressed. Consequently, the bias-stress stability of GaSb nanowire field-effect transistors (NWFETs) with AlOxshells exhibits significant improvement. These devices displayed minimal attenuation of the on-state current (within 10%) and a negligible negative shift in threshold voltage under 60 minutes of continuous gate bias, which is far better than that of pristine GaSb NWFETs. When configured into a near-infrared photodetector, the as-constructed AlOx-shelled NWFET with enhanced bias-stress stability demonstrates anticipated gate-controlled photodetection imaging and photocommunication ability. The related results entitled "Toward high bias-stress stability p-type GaSb nanowire field-effect-transistor for gate-controlled near-infrared photodetection and photocommunication" have been published inAdvanced Functional Materials(2023, 33, 2304064).

Fig. 2 Regulation of the surface states of antimonide NWs using a low-temperature solution-annealing method and the gate-controlled infrared photodetection performance.

Process 3. Inhibit the charge-trapping effect of the surface states by charge compensation of the mobile oxygen ions in the surface oxide layer.

The prevalence of Si and its associated processes in mainstream technology can be attributed, in part, to the capability of forming a high-quality dielectric SiO2 layer on its surface. In contrast, antimonide NWs often possess a 2-5 nm natural oxide layer on their surface, contributing to the existence of surface charge traps that compromise the bias-stress stability of NWFETs.Recently, Yang Zaixing and his team achieved precise control over the oxide layer thickness on antimonide NWs through in-situ annealing in the atmosphere. Leveraging the charge compensation provided by mobile oxygen ions in the surface oxide layer, the researchers successfully mitigated the surface charge traps of antimonide NWs. The resultant antimonide NWFET, featuring the oxide layer, exhibits outstanding stability, characterized by a minimal shift in the transfer curve (ΔVth≈ 0.54 V), which is far more stable than that of pristine GaSb NWFET. Moreover, the presence of mobile oxygen ions in the oxide layer holds promise for advancing the potential applications of antimonide NWs in future neuromorphic computing systems. This work entitled "An Amorphous native oxide shell for high bias-stress stability nanowire synaptic transistor" has been published in Advanced Science(2023, 10, 2302516).

Fig. 3 Construction of high bias-stress stability antimonides NWFETs by charge compensation of mobile oxygen ions in the surface oxide layer.

Process 4. Develop a new metal-assisted transfer approach to overcome the Fermi level pinning effect.

Owing to the Fermi level pinning effect, metal-semiconductor contact is always independent of the work function, which challenges the next-generation optoelectronic devices. Typically, this pinning effect arises from surface states in low-dimensional semiconductors and the diffusion of metal atoms during the deposition of metal electrodes. To circumvent metal atom diffusion into semiconductors during metal electrode deposition, metal electrodes can be transferred onto low-dimensional materials. Alternatively, low-dimensional semiconductors can be directly transferred onto pre-deposited metal electrodes. In a pioneering advancement, Yang et al. introduced a metal-assisted transfer approach to fabricate room-temperature high-performance infrared photodetectors. The method capitalizes on robust van der Waals forces between metals and low-dimensional semiconductors. Through this metal-assisted transfer approach, low-dimensional semiconductors grown in situ can be directly transferred onto substrates with pre-deposited electrodes. This technique sidesteps metal atom diffusion during deposition, preserves the perfect surface of low-dimensional semiconductors, and mitigates the surface Fermi level pinning effect. Consequently, it allows for the tunability of metal-semiconductor contact barriers. By strategically selecting metals with varying work functions as electrodes, the approach enables the construction of Ohmic contact, Schottky contact, and asymmetric contact infrared photodetectors with remarkable success. Notably, the convenience of the as-developed metal-assisted transfer approach enables the construction of infrared photodetectors on arbitrary substrates, demonstrating high-performance flexible and omnidirectional self-powered near-infrared photodetectors. This work entitled "Tunable contacts of Bi₂O₂Se nanosheets MSM photodetectors by metal-assisted transfer approach for self-powered near-infrared photodetection" has been published in Small (2023, 19, 2306363).

Fig. 4 Developing a metal-assisted transfer approach for constructing room-temperature high-performance infrared photodetector.

The above results provide a new way to regulate the surface state of semiconductors and promote the development of next-generation high-performance field-effect transistors and high-performance room-temperature infrared photodetection. Yang et al. thank Prof. Johnny C. Ho from the City University of Hong Kong, Prof. Chen Feng from the School of Physics, Prof. Liao Lei from Hunan University, Prof. He Longbing from Southeast University, and Prof. Song Kepeng from Core Facilities Sharing Platform for their careful guidance and support. These works are supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Taishan Scholars Program of Shandong Province, and the Shandong Provincial Natural Science Foundation.

Article links:

https://doi.org/10.1038/s41467-023-43323-x

https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202304064

https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202302516

https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.202306363