Source/Drain Asymmetry in InGaAs Vertical Nanowire MOSFETs

This paper demonstrates InGaAs vertical nanowire (VNW) MOSFETs fabricated via an improved top-down approach, the performance of which is comparable to that of the best bottom-up devices in terms of the balance between transport and electrostatics. These devices, when contrasted with an earlier generation fabricated by a similar technology, have enabled the first experimental study of source/drain asymmetry in InGaAs VNWMOSFETs. The transconductance differs significantly when swapping source and drain due to inherently different top and bottom contact electrical resistance. This also results in distinct asymmetry in the saturation behavior of the output characteristics. On the other hand, diameter nonuniformity along the nanowire (NW) length is responsible for asymmetry in the subthreshold characteristics. A uniform NW cross section, enabled by our improved InGaAs dry etch technology in the present devices, eliminates the asymmetry of the electrostatics, which was observed in our previous work.