Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: Doped Si nanostructures (DS with HL/TT)

HL 27.5: Invited Talk

Tuesday, March 17, 2015, 11:30–12:00, H 2032

Doping issues in semiconductor field-effect transistors — •Joachim Knoch — Institute of Semiconductor Electronics, RWTH Aachen University, Aachen, Germany

The functionality of silicon devices such as transistors, solar cells etc. rely on the ability to create doping profiles. However, due to the continued downscaling of device dimensions doping becomes increasingly difficult due to a number of fundamental reasons. First, dopants will be statistically distributed within the silicon nanostructures leading to a dopant fingerprint that results in fluctuations of e.g. electronic transistor characteristics from device to device. Second, studying the resistivity of in-situ doped, VLS-grown nanowires we were able to show that with decreasing nanowire diameter the resistivity increases due to a deactivation of dopants. The reason for the deactivation was shown to be the modified effective dielectric environment if the nanowire diameter is scaled down. In turn, the deactivation results in larger parasitic resistances of the contacts of e.g. transistors, substantially deteriorating their performance. Third, ultimately scaled conventional field-effect transistors (FETs) and in particular novel device architectures such as band-to-band tunnel FETs require extremely small nanowire diameters and eventually lead to one-dimensional (1D) electronic transport. While 1D transport is beneficial to conventional FETs, in the case of tunnel FETs the 1D density of states leads to an inability of appropriate doping (even if deactivation and the statistical dopant distribution could be avoided). The effects will be discussed particularly with respect to their impact on device functionality.