Solid-state diffusion as an efficient doping method for silicon nanowires and nanowire field effect transistors

Abstract

In this work we investigate doping by solid-state diffusion from a doped oxide layer, obtained by plasma-enhanced chemical vapor deposition (PECVD), as a means for selectively doping silicon nanowires (NWs). We demonstrate both n-type (phosphorous) and p-type (boron) doping up to concentrations of 10(20) cm(-3), and find that this doping mechanism is more efficient for NWs as opposed to planar substrates. We observe no diameter dependence in the range of 25 to 80 nm, which signifies that the NWs are uniformly doped. The drive-in temperature (800-950 °C) can be used to adjust the actual doping concentration in the range 2 × 10(18) to 10(20) cm(-3). Furthermore, we have fabricated NMOS and PMOS devices to show the versatility of this approach and the possibility of achieving segmented doping of NWs. The devices show high I(on)/I(off) ratios of around 10(7) and, especially for the PMOS, good saturation behavior and low hysteresis.

Individualization and Electrical Characterization of SiGe Nanowires

“…Different Ge atomic fractions (from 0 to -15 %) were obtained by changing the flow ratio (R) of the GeH 4 and SÍ2H 6 precursor gases. Doping (n-type) of the NWs was carried out by diffusion using two approaches [11,12]. First, a spin-on glass containing P was deposited on the samples and densified, in such way that the NWs were encapsulated by the dopant source during the subsequent annealing step [13].…”

InP nanowire p-type doping via Zinc indiffusion

“…As a result, creating ohmic contacts to the p-type InP NWs becomes increasingly difficult the lower the doping 9 . An alternative pathway for doping is indiffusion of dopants from gas phase at high temperatures, which has been extensively studied for thin films [9][10][11][12][13][14][15][16] , but has been applied to NWs only recently for materials including InAs 17,18 , Si 19,20 and ZnO 21 . With diffusion doping, electrical transparency to the NW contacts can be increased significantly via high carrier concentrations near the surface 17,19 .…”

“…Additionally, site selective doping can be performed, e.g. by covering selected parts of the NWs 17,19 .…”

Fabrication and doping of silicon micropillar arrays for solar light harvesting

“…PH 3 ), they form highly reactive chemical species that produce the desired layer, already at a temperature of 300 °C. [70] PECVD can also be used to deposit in-situ doped silicon, by means of which the drive-in step can be omitted, but it yields an amorphous or poly-crystalline layer. [71,72] Hot-wire chemical vapor deposition (HWCVD), also referred to as catalytic CVD, is used for the deposition of mainly inorganic thin films.…”

“…Atmospheric-pressure CVD [3,66,103] No Yes 100-3000 Yes Plasma-enhanced CVD [68,70,72] Yes Yes 100-3000 Yes…”