Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 48: ZnO: Devices
HL 48.3: Talk
Wednesday, March 16, 2011, 10:45–11:00, POT 151
Carrier transport in nanocrystalline field-effect transistors: Impact of interface roughness and geometrical carrier trap — •Koshi Okamura and Horst Hahn — Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany
Nanocrystalline field-effect transistors (FETs) inherently have a certain level of roughness at the semiconductor-dielectric interface, which originates from the size of building blocks, i.e., nanocrystals ranging from a few to a few tens of nanometers. This interface roughness is expected to act like carrier traps, significantly preventing induced carriers from being transported along the channel in nanocrystalline FETs. In this study, a simple numerical calculation is performed for nanoparticulate zinc oxide (ZnO) FETs on the basis of Shockley’s gradual channel approximation with the induced carriers classified into two components: (1) fixed carriers located within a threshold depth dth from the interface and (2) mobile carriers located away from dth. This calculation clearly indicates that the mobile carrier concentration is strongly dependent on the level of interface roughness; and the field-effect mobility is directly reflected by the mobile carrier concentration, significantly decreasing by a factor of 3.9x10−1, 7.4x10−2, 3.0x10−2, 3.9x10−3, and 7.3x10−4 for dth of 1, 5, 10, 30, and 40 nm, respectively. These findings reveal that an interface roughness as small as a few nanometers results in a decrease in field-effect mobility as large as an order of magnitude, which is in qualitative agreement with experimental results.