A General Approach to Probe Dynamic Operation and Carrier Mobility in Field‐Effect Transistors with Nonuniform Accumulation

Abstract

Revealing the intrinsic electrical properties is the basis of understanding new functional materials and developing their applications. However, in nonideal field-effect transistors (FETs), conventional current-voltage characterizations do not accurately probe charge transport, particularly for newly developed semiconductors. Here, a generalized gated four-probe (G-GFP) technique is developed, which detects dynamic changes in carrier accumulation and transport. The technique is suitable for exploring the intrinsic properties of semiconductors in FETs with arbitrary contacts and in any operational regimes above the threshold. Application to simulated transistors confirms its accuracy in probing the evolution of channel potential, drift field, and gate-dependent carrier mobility for devices with a contact-limited operation and disordered semiconductors. Comparative experiments are performed based on FETs with various materials, device structures, and operational temperatures. The G-GFP technique proves to exclude the various injection properties, to detect in situ how carriers are accumulated, and to clarify carrier mobility of the semiconductors. In particular, the well-known "double-slope" features in the current-voltage relations are controllably generated and their origins are identified. The approach could be used to explore electronic properties of newly developed materials such as organic, oxide, or 2D semiconductors.

P‐1.10: Mobility identification in oxide field‐effect transistor

“…To clarify this situation, we developed the generalized gated-four point method (GGFP) to exclude the contact effects and identify the intrinsic mobility in all operation regimes by detecting the channel potential insitu. Experimental and simulated results confirmed the accuracy and applicability of the proposed method [4].…”

Understanding, Optimizing, and Utilizing Nonideal Transistors Based on Organic or Organic Hybrid Semiconductors

“…With one extra moving probe (for SKPM) or two fixed‐voltage probes (for GFP) in the channel, the experiments can help identify the voltage drop in the channel and estimate the carrier concentration n . The generalized GFP can be used for arbitrary regimes in FETs . 3) Measuring the Hall effect in gated devices by magnetic interaction.…”

“…Moreover, both types of factors could lead to positive or negative shifts of V th (or even nonconstant V th during measurements) and changed current levels. The complicated V th has been discussed in detail in the literature and could be read from G‐GFP measurements. Alternatively, V th could be extracted from I – V characteristics by referencing to that in inorganic FETs …”

“…d) Measured potential and carrier concentration in offset‐gated FETs at 238 K by G‐GFP measurement, which show direct evidence of nonlinear n – V G relations. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

“…In the saturated regime with a large V D , the value of V 0 across the depletion region can be tuned in a large range accompanied by the change in the tunneling barrier near the source electrode. Because SKPM requires a delicate experimental setup and wire‐bonding, the gated four‐probe measurement for the linear regime and its generalized form G‐GFP covering the nonlinear and saturated regime is an important alternative to probing V ( x ). While SKPM can detect V ( x ) in FETs at certain V G and V D , G‐GFP is capable of detecting and evaluating the dynamic evolution of V ( x ), n , and E X during scanning of the device (Figure d).…”