Boron distributions in individual core–shell Ge/Si and Si/Ge heterostructured nanowires

Bin Han,Jevasuwan Wipakorn,Naoki Fukata,Yasuo Shimizu,Yasuyoshi Nagai,Koji Inoue,Yuan Tu,Kotaro Nishibe

doi:10.1039/c6nr04384d

Bin Han, Jevasuwan Wipakorn + Show 6 more

Open Access

https://doi.org/10.1039/c6nr04384d

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Abstract

Ge/Si and Si/Ge core-shell nanowires (NWs) have substantial potential for application in many kinds of devices. Because impurity distributions in Ge/Si and Si/Ge core-shell NWs strongly affect their electrical properties, which in turn affect device performance, this issue needs urgent attention. Here we report an atom probe tomographic study of the distribution of boron (B), one of the most important impurities, in two kinds of NWs. B atoms were doped into the Si regions of Ge/Si and Si/Ge core-shell NWs. It was found that the B atoms were randomly distributed in the Si shell of the Ge/Si core-shell NWs. In the Si/Ge core-shell NWs, on the other hand, the B distributions depended on the growth temperature and the B2H6 flux. With a higher growth temperature and an increased B2H6 flux, the B atoms piled up in the outer region of the Si core. However, the B atoms were observed to be randomly distributed in the Si core after decreasing both the growth temperature and the B2H6 flux.

Highlights

IntroductionConsiderable research has been carried out on investigating silicon (Si) and germanium (Ge) based semiconductor nanowires (NWs), owing to their substantial potential for application in many kinds of devices, such as metal– oxide–semiconductor field-effect transistors, and their compatibility with the current semiconductor technology.[1,2,3,4,5] In particular, Ge/Si and Si/Ge core–shell NWs have attracted special attention because of the band offset effect between Ge and Si.[6,7,8,9,10] In Ge/Si and Si/Ge core–shell NWs, the impurity can be selectively doped into either the core or shell region
The B distributions in Ge/Si and Si/Ge core–shell NWs were studied by atom probe tomography (APT)
B atoms were precisely doped into the Si regions of Ge/Si and Si/Ge core–shell NWs, and did not diffuse into the Ge regions

Summary

Introduction

Considerable research has been carried out on investigating silicon (Si) and germanium (Ge) based semiconductor nanowires (NWs), owing to their substantial potential for application in many kinds of devices, such as metal– oxide–semiconductor field-effect transistors, and their compatibility with the current semiconductor technology.[1,2,3,4,5] In particular, Ge/Si and Si/Ge core–shell NWs have attracted special attention because of the band offset effect between Ge and Si.[6,7,8,9,10] In Ge/Si and Si/Ge core–shell NWs, the impurity can be selectively doped into either the core or shell region. Due to the band offset effect, impurities and carriers are separated in the core and shell regions, which markedly reduces the carrier scattering rate.[11,12,13] the characterization of impurity distributions in Ge/Si and Si/Ge core–shell NWs is an important issue. Our APT results demonstrate that the B atoms were randomly distributed in the Si shell of Ge/Si core–shell NWs. On the other hand, in Si/ Ge core–shell NWs, B piled up in the outer region of the Si core. Similar processes were performed for the second kind of Si/Ge core–shell NWs, but the flux gas of B2H6 (1%), growth temperature, and time were changed to 0.2 sccm, 600 °C, and 30 min, respectively, when growing the B-doped Si core.[20]. An integrated visualization and analysis software (IVAS) protocol was employed to reconstruct the 3D atomic maps.[35]

Results and discussion

Conclusions