Growth and Electrical Applications of InAsSb Nanowires


Student thesis: Doctoral Thesis

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Awarding Institution
Award date6 Dec 2018


Nowadays, the demand for high-speed electronics keeps on surging because of the increasing accessibility of the internet and the development of applications like AI and big data analysis. On the other hand, mid-IR sensing (2µm to 5µm) is also an intriguing aspect that attracts tremendous research effort. For these two applications, InAs and InSb and their ternary alloy InAs1-xSbx sit as a prime candidate due to their high electron mobility and direct band gap which fits in the mid-IR range. Their nanowire (NW) counterpart is relatively less studied. In this thesis, the InAs1-xSbx NWs were studied.

In the second chapter of this thesis, InAsxSb1-x NWs were grown on an amorphous substrate with the aid of solid-source CVD (SSCVD) covered by a thin gold layer (~0.5nm) which was used as the catalyst. The composition of InAsxSb1-x NWs was tuned by changing the weight ratio of the InAs and InSb powder used in NWs growth. The highest x achieved in this chapter is 0.2. With increasing Sb incorporation, the NWs dimensions were changed accordingly. The crystal structure was also studied. The InAs1-xSbx NWs were found to be dominant by zinc blend phase while no significant amount of wurtzite phase was found.

In chapter 3, a method has been developed to enhance the Sb incorporation as well as the obtained NW length for higher Sb concentration. That is, instead of using a complete Au film, Au islands were created by scratching the Au thin film. At the edge of the Au island, the InAsxSb1-x nanowire was found to longer and have better morphology. With this technique, InAs1-xSbx NWs with x up to 0.3 were achieved. The obtained NWs were also found to be zinc blend dominated. The mechanism behind the growth rate enhancement was studied.

In chapter 4, pure InAs and InAs0.95Sb0.05 NWs obtained in the previous chapter were integrated into a back-gated transistor structure. The electrical performance was accessed and the electron mobility of InAs0.95Sb0.05 NWs is as high as 6000 cm2V−1s−1 which is highest among the reported with similar composition. The high mobility is attributed to the good crystal quality. Despite the high mobility, the rapid drop of on-off ratio leaves a room for further improvement in the future.