One-Dimensional Nanostructures and Devices of II–V Group Semiconductors
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The II–V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn3P2nanowires, one-dimensional (1-D) nanostructures of II–V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II–V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures will also be discussed, which include metal–insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, andp–n heterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities.
KeywordsNanowires Nanotubes Nanobelts Semiconductors Nanoelectronics
Because of the ability to synthesize them in numerous configurations and their unique physical, chemical, optical, electrical, and magnetic properties, one-dimensional (1-D) nanostructures have attracted great interest in recent years [1–5]. 1-D nanostructures play important roles both as interconnect and functional units in fabricating nanoscale electronic, optoelectronic, electrochemical, and electromechanical devices. 1-D nanostructures have been synthesized for a lot of materials, including metals, II–VI and III–V semiconductors, sulfides, nitrides, etc., using a variety of synthetic techniques, such as solution process, vapor–solid process, vapor–liquid–solid process, template-directed process and so on [6–40].
Semiconducting II–V compounds are important narrow band gap semiconductors with great scientific and technological importance . They are suggested to exhibit pronounced size quantization effects due to the large excitonic radii. Bulk II–V semiconductors have been used as infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators [42–50]. However, research on nanoscale II–V semiconductors, especially 1-D nanostructures, has been lingering far behind compared with the significant progress in the studies of 1-D II–VI and III–V semiconductors, mainly due to the significant synthetic experimental difficulties, such as lack of generalized synthetic methodologies, instability in air, etc. Since the first successfully synthesized trumpet-like Zn3P2 nanowires in 2006, many kinds of interesting 1-D II–V semiconductors nanostructures have been reported using different techniques, which greatly promote their further application in nanoscale electronic and optoelectronic devices.
This article will provide a comprehensive review of the state-of-the-art research activities focused on synthesis and devices of 1-D II–V semiconducting nanostructures. The first section introduces typical 1-D nanostructures obtained on II–V semiconductors, including nanotubes, nanowires, nanobelts, and some special nanostructures. Next, some important electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures are presented, which include metal–insulator-semiconductor field-effect transistors (MIS-FET), metal-semiconductor field-effect transistors (MS-FET), andp–n heterojunction photodiode. This review will then conclude with some personal perspectives and outlook on the future developments in the 1-D II–V semiconducting nanostructures research area.
Typical 1-D Nanostructures of II–V Group Semiconductors
Since the first successfully synthesized trumpet-like Zn3P2nanowires in 2006, many kinds of interesting 1-D II–V semiconducting nanostructures, such as nanotubes, nanowires, and nanobelts, special nanostructures have been reported using different techniques. In this section, we will discuss several typical 1-D nanostructures obtained on II–V semiconductors.
Liu et al.  reported the synthesis of Zn3P2 nanowires by the reaction between Zn and InP powders at 850 °C. These Zn3P2 nanowires are also single crystals and have typical diameters of about 100 nm and lengths of tens of microns, as revealed in Fig. 3b. During this process, Au was used as catalysts to direct the nanowire growth and it is obviously a vapor–liquid–solid (VLS) process.
Special 1-D Nanostructures
Synthesis and assembly of 1-D nanostructures with special morphologies, shapes, and compositions have attracted great interests very recently because they may process interesting physical and chemical properties associated with their specific characteristics. They may also be used to fabricate special electronic and optoelectronic devices which cannot be fulfilled using simple 1-D nanostructures.
We have discussed above several kinds of 1-D II–V semiconducting nanostructures obtained till now. By carefully controlling the experimental parameters, such as evaporation sources, temperature, carrier gases, etc., more 1-D nanostructures are expected to be obtained for II–V group semiconductors.
Device Applications of 1-D II–V Semiconducting Nanostructures
As an important group of narrow band gap semiconductors, 1-D II–V semiconducting nanostructures can be used to fabricate nanoscale electronic and optoelectronic devices. Several kinds of nanodevices had been fabricated built on single 1-D II–V semiconducting nanostructure, such as MIS-FET, MS-FET, andp–n heterojunction photodiode.
MIS-FET Built on Single 1-D II–V Semiconducting Nanostructures
To investigate the electronic transport behaviors of 1-D II–V semiconducting nanostructures, we fabricated MIS-FET built on single Zn3P2 and Cd3P2 bicrystal nanobelts and explored the electronic transport behaviors as a function of temperature in vacuum . A SEM image of the Zn3P2 MIS-FET is depicted in Fig. 8c inset. Figure 8c displays the I–V curves of a Zn3P2 bicrystal nanobelt MIS-FET device measured in the temperature region of 100–300 K without applying gate voltage. The conductance of the device continuously decreased as the temperature decreased. The zero-bias conductance at 300 K is calculated to be 27.75 nano-Siemens (nS) and it decreases to 0.01 nS at 100 K. Plotted the zero-bias conductance in a logarithmic scale as a function of 1000/T gives a linear behavior within the temperature region investigated. All these results suggested that the thermal activation of carriers is the dominant transport mechanism for the Zn3P2 bicrystal nanobelt MIS-FET. The electronic transport behavior of Cd3P2 bicrystal nanobelts was also investigated at different temperatures and the results (Fig. 8d) also suggested a dominant thermal activation of carriers transport mechanism.
MS-FET Built on Single 1-D II–V Semiconducting Nanostructures
p–n Heterojunction Photodiode Built with Zn3P2Nanowires and ZnO Nanowires
In conclusion, we provide a comprehensive review of the state-of-the-art research activities focused on the synthesis and device applications of 1-D II–V semiconducting nanostructures. The rapid expended achievements, till now, toward 1-D II–V semiconducting nanostructures should inspire more and more research efforts to address the remaining challenges in this interesting filed.
Although comprehensive efforts have been made toward the synthesis of high-quality 1-D II–V semiconducting nanostructures, there is still plenty of room left unexploited. We believe that future work should continue to focus on generating them in more controlled, predictable, and simple ways. The II–V semiconductors exhibit pronounced size quantization effects due to the large excitonic radii, thus, it is important to synthesize 1-D II–V semiconducting nanostructures with diameters smaller than the excitonic radii. For example, one needs to find ways to get II–V semiconducting nanotubes with either very small diameter or very thin wall thickness. The physical and chemical properties of II–V semiconducting nanostructures with diameters smaller than the excitonic radii will then need to be investigated and more interesting results are expected to be gotten soon.
Besides, more functional nanoscale electronic and optoelectronic devices are expected to be built on 1-D II–V semiconducting nanostructures and the performance of the devices will be largely improved with the progress of producing high-quality 1-D II–V semiconducting nanostructures.
The authors acknowledge financial support from the High-level Talent Recruitment Foundation of Huazhong University of Science and Technology. The authors acknowledge the permission from the corresponding publishers/groups to reproduce their materials, especially figures, used in this paper.