H. H. Choi, K. Cho, C. D. Frisbie, H. Sirringhaus and V. Podzorov, Critical assessment of charge mobility extraction in FETs, Nat Mater, 2018, 17(1): 2. (DOI: https://doi.org/10.1038/nmat5035)

要点

迁移率正确的表征方法

Shockley equations

物理机理前提

linear relationship between the carrier density n n n and conductivity σ σ σ: σ = μ e n σ = μen σ=μen.

gradual channel approximation

(a) the transverse gate electric field is much greater than the longitudinal source–drain electric field，
(b) the mobility is carrier density independent

电场强度gate方向>>source-drain方向；载流子浓度无关的迁移率。

提取方法前提

Equations (1) and (2) are only applicable when dependences I S D ( V G ) I_{SD}(V_G) ISD​(VG​) in the linear regime and ∣ I S D ∣ 1 / 2 ( V G ) |I_{SD}|^{1/2}(V_G) ∣ISD​∣1/2(VG​) in the saturation regime are linear in an extended range of V G V_G VG​.

接触电阻和短沟道效应的影响

provided that other extrinsic sources of error, such as short-channel effects or high contact resistance, are excluded

无序系统

无序系统，迁移率与载流子浓度有关。
In disordered systems, μ could be carrier-density dependent (for instance, due to band-tail filling)

Y. Xia, J. H. Cho, J. Lee, P. P. Ruden and C. D. Frisbie, Comparison of the Mobility-Carrier Density Relation in Polymer and Single-Crystal Organic Transistors Employing Vacuum and Liquid Gate Dielectrics, ADVANCED MATERIALS, 2009, 21(21): 2174. (DOI: https://doi.org/10.1002/adma.200803437)

非线性

Nonlinearities in Fig. 1a–c might have diverse microscopic origins (partially discussed in the recommendations below), including contact effects, carrier density-dependent mobility and nonequilibrium biasing of short-channel OFETs.

the hump originates from gated Schottky contacts, and the intrinsic carrier mobility corresponds to the plateau.

Similarly, double-slope characteristics in donor– acceptor polymer FETs, originating from minority carrier injection and trapping

T. Okachi, T. Kashiki and K. Ohya, Device operation mechanism of field-effect transistors with high mobility donor-acceptor polymer semiconductors, Proc Spie, 2015, 9568((DOI: https://doi.org/10.1117/12.2187572)

increased contact resistance strongly suppresses the current at low V G V_G VG​ but leads to a more rapid increase in I S D I_{SD} ISD​ at higher V G V_G VG​, hence resulting in overestimation of mobility.

reliability factor

μ e f f ≡ r × μ c l a i m e d μ_{eff} ≡ r × μ_{claimed} μeff​≡r×μclaimed​