Design, Synthesis and Properties Study of Ternary InGaSb Nanowires
Student thesis: Doctoral Thesis
Related Research Unit(s)
III-V semiconductor nanowires (NWs) have attracted significant attention, due to their novel mechanical, optical, and electronic properties that are not present in the thin film counterparts and diverse types of NW-based devices have been demonstrated across a wide range of areas, such as electronics, photonics, biochemistry, and medicine. To date, because of the unique bandgap tuning properties and incredible electrical characteristics, ternary III-V nanowires (NWs) have been demonstrated with enormous potential for advanced electronics and optoelectronics, there are many of experimental investigations with the aim to control the composition and study the applications in ternary III-V NWs, and perhaps the most investigated ternary NW systems are InGaAs, InGaSb, AlGaAs, InAsSb, and GaAsSb, however, the synthesis of largescale and highly crystalline InGaSb NWs in a controllable low-cost manner is still a substantial challenge, there are only fewer and fewer of work focused on ternary InGaSb system NWs, in those existing work, they mainly investigated the ternary/binary heterostructure NWs, the pure and uniform ternary InGaSb system NWs with excellent photoelectrical properties and controlled stoichiometry have not been well investigated.
In this dissertation, the successful synthesis of the pure and uniform ternary stoichiometric InGaSb NWs is presented by two-step chemical vapor deposition method growth method and novel Sb-film-assist CVD growth method, and their opt electric properties and applications has also been investigated.
In chapter 2, that is the experimental part, we describe the growth methods to obtain the InGaSb NWs, and detail processes to fabricate the FET devices, Photodetector devices and Flexible devices.
For the InGaSb NWs, difficulties still exist in synthesis of stoichiometry controllable ternary NWs, such as crystal quality and uniform diameter distribution, more importantly, the understanding of the relationship between stoichiometry and growth parameter. In chapter 3, for the first time, we successfully achieve high-density and crystalline stoichiometric InxGa1-xSb NWs on amorphous substrates with the uniform phase-purity and <110>-orientation via two-step CVD method. The as-prepared NWs show excellent electrical properties, including the record-high hole mobility (i.e. 463 cm2V-1s-1 for In0.09Ga0.91Sb NWs). Importantly, when configured into photodetectors, they exhibit impressive broadband and ultra-fast photoresponse over the visible and infrared optical communication region (1550 nm). For example, the In0.28Ga0.72Sb NW device can yield the efficient rise and decay times down to 38 and 53 μs, respectively, along with the excellent responsivity of 6000 A/W, external quantum efficiency of 4.8×106 % and specific detectivity of 3.7×109 Jones towards the 1550 nm regime, this is the first time to achieve microsecond order near-infrared NWs photodetector at room temperature. Moreover, high-performance NW parallel array devices can also be fabricated to illustrate their technological potency for large-scale device integration. All these results evidently reveal these InxGa1-xSb NWs as promising materials for the next generation, ultra-fast, high-responsivity and broadband photodetectors.
1-D inorganic semiconductors have great superiorities to construct flexible and wearable electronic devices, such as photodetector, pressure sensors and gas/chemical sensors, there are significant challenges in integrating these multifunctional NWIIarrays, fabricating and evaluating the performance limits of the photodetector circuit matrix based on these synthetic nanostructures. Also, the InGaSb NWs are being actively explored as a candidate material for flexible and stretchable devices. However, the development of InGaSb-based flexible photonic devices is slowly. Here, in chapter 4, we report for the first time, a flexible InGaSb NW arrays photodetector with a high photo-responsivity of ~1520 AW-1 and a fast response time of ~10 μs under 1550nm laser at room temperature. In addition, the device exhibits good robustness against repetitive bending, suggesting its applicability in large-area matrix-array flexible photodetectors.
Although the results are interest, but the range of Indium concentration in the InGaSb system NWs obtained by two-step chemical vapor deposition growth method is narrow, so that it is hard to study the more and furthermore properties, hence to obtain the In-rich InGaSb NWs is one challenge to study the ternary InGaSb system NWs. In chapter 5, we emphasize on the synthesis of ternary InGaSb NWs by one novel Sb- film-assist CVD growth method and the applications in photodetector system, the In- rich InGaSb NWs were obtained for the first time, that the Indium concentration was improved to 51 percentages in the InGaSb NWs by the novel growth method, the In- rich In0.51Ga0.49Sb NWs exhibited bipolar semiconductor nature with the peak electronic mobility 225 cm2V-1s-1 and hole mobility 46 cm2V-1s-1, and good performance for near-infrared photodetection.
Finally, Chapter 6 concludes my PhD studies on InGaSb NWs with respect to two step CVD growth method and novel Sb-film-assist CVD growth method, detailed structural characterizations and optoelectrical properties as well as the study of theIIIapplication of room temperature Vis to IR photodetector device based on the ternary InGaSb NWs. All these results would provide a valuable insight in achieving high-performance III-V NWs for technological applications.