Effect of HCl on the doping and shape control of silicon nanowires

Abstract

The introduction of hydrogen chloride during the in situ doping of silicon nanowires (SiNWs) grown using the vapor-liquid-solid (VLS) mechanism was investigated. Compared with non-chlorinated atmospheres, the use of HCl with dopant gases considerably improves the surface morphology of the SiNWs, leading to extremely smooth surfaces and a greatly reduced tapering. Variations in the wire diameter are massively reduced for boron doping, and cannot be measured at 600 °C for phosphorous over several tens of micrometers. This remarkable feature is accompanied by a frozen gold migration from the catalyst, with no noticeable levels of gold clusters observed using scanning electron microscopy. A detailed study of the apparent resistivity of the NWs reveals that the dopant incorporation is effective for both types of doping. A graph linking the apparent resistivity to the dopant to silane dilution ratio is built for both types of doping and discussed in the frame of the previous results.

Geometrical control of photocurrent in active Si nanowire devices

“…The solution was then dropcasted on the Si wafer with 200 nm thick thermal silicon oxide (SiO 2 ). No gold removal process was performed prior to drop casting, owing to the peculiar nature of HCl assisted growths that were found to suppress any catalyst loss from the NW head, as described in [16][17]. Further optical lithography was performed on the above samples by spin coating with MAN 2410 photoresist followed by deep UV exposure and subsequent developing.…”

Fabrication and characterization of silicon nanowire p-i-n MOS gated diode for use as p-type tunnel FET

“…It is worth noting that the dc/dv intensity is constant along each segment indicating a uniform doping level. This uniform doping is related to the use of HCl during the growth which prevents the radial growth and the formation of superdoped shell [17]. Thanks to this SCM measurement, we know that the p-type and n-type doping levels are high enough to avoid a large resistance contact at the drain and source regions.…”

“…The growth was performed at 600 C under a total pressure of 3 Torr using silane ðSiH 4 Þ and HCl as reactive gases with flows of 40 and 100 sccm, respectively. The flow of HCl was maintained throughout the entire growth process in order to prevent uncatalysed 2D growth and gold diffusion from the catalyst along the axis of SiNW [17].…”

Diamond-coated silicon wires for supercapacitor applications in ionic liquids

“…The wires are heavily p-type doped (N A =~4×10 19 cm -3 ) [16], with a diameter of ~50 nm and a length of ~5 µm. The density of the nanowires is estimated by counting the number of gold colloids per cm 2 on several SEM images [17], and the number is about 3×10 8 cm -2 .…”