Controlling Axial p-n Heterojunction Abruptness Through Catalyst Alloying in Vapor-Liquid-Solid Grown Semiconductor Nanowires
The p-n junction can be regarded as the most important electronic structure that is responsible for the ubiquity of semiconductor microelectronics today. Efforts to continually scale down the size of electronic components is guiding research to explore the use of nanomaterials synthesized from a bottom-up approach - group-IV semiconductor nanowires being one such material. However, Au-catalyzed synthesis of Si/Si1-x-Gex semiconductor nanowire heterojunctions using the commonly-used vapor-liquid-solid (VLS) growth technique results in diffuse heterojunction interfaces [1], leading to doubts of producing compositionally-sharp p-n junctions using this approach. However, we have recently reported the ability to increase Ge-Si nanowire heterojunction abruptness by VLS synthesis from a Au(1-x)Ga(x) catalyst alloy as shown by EDX analysis in an SEM [2]. In this work, we have extended the use of a AuGa catalyst alloy to produce more compositionally abrupt p-n junction interfaces compared to using pure Au as directly measured by atom probe tomography. As shown in Figure 1(a-b), individual Ge-Si heterostructured nanowires were grown vertically atop Ge(111) microposts. Direct growth on the microposts provides a facile approach to nanowire analysis which circumvents the need to use FIB-based sample preparation techniques. Both nanowires grown from pure Au and a AuGa catalyst alloy were analyzed. The corresponding 3D APT reconstruction of an individual heterostructured nanowire is shown in Figure 1(c) with the corresponding materials labeled. A 1-dimensional composition profile along the analysis direction in Figure 1(d) confirms an increase in heterojunction abruptness for nanowires grown from AuGa (~10nm) compared to nanowires grown from pure Au (~65nm). Analysis of the P distribution within the Si region (Figure 1(e)) indicates that P reaches a constant distribution over approximately 10nm when incorporated through the AuGa catalyst, whereas it continually increases over 100’s of nanometers when incorporated through pure Au. The apparent lower overall P concentration within the nanowire grown from the AuGa alloy suggests that the solubility of P in the alloy is lower compared to pure Au. The ability to controllably increase nanowire p-n junction abruptness is important for nanowire applications as solar cells and tunneling field effect transistors where an increase in device performance is expected from shaper p-n junction interfaces. [1] T.E. Clark et al., Nano Lett. 8 (2008) 1246. [2] D.E. Perea et al., Nano Lett. 11 (2011) 3117. [3] The research was supported through the user program at both the Center for Integrated Nanotechnologies at Los Alamos National Laboratory and the Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1148635
- Report Number(s):
- PNNL-SA-91518; 46696; KP1704020
- Journal Information:
- Microscopy and Microanalysis, 18(Suppl. 2):1860-1861, Journal Name: Microscopy and Microanalysis, 18(Suppl. 2):1860-1861
- Country of Publication:
- United States
- Language:
- English
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