Mobility and Threshold Voltage Extraction in Transistors with Gate-Voltage-Dependent Contact Resistance

TL;DR

This paper introduces a new method to accurately extract mobility in transistors with gate-dependent contact resistance, especially useful for emerging devices where traditional methods fail due to contact gating effects.

Contribution

The authors develop an updated transfer length method that accurately measures mobility without high gate bias, addressing contact gating issues in emerging transistors.

Findings

Achieves less than 10% error in mobility extraction.

Corrects overestimation of mobility by more than 2 times in conventional methods.

Effective in devices with high contact resistance and early dielectric breakdown.

Abstract

The mobility of emerging (e.g., two-dimensional, oxide, organic) semiconductors is commonly estimated from transistor current-voltage measurements. However, such devices often experience contact gating, i.e., electric fields from the gate modulate the contact resistance during measurements, which can lead conventional extraction techniques to estimate mobility incorrectly even by a factor >2. This error can be minimized by measuring transistors at high gate-source bias, |$V_\mathrm{gs}$|, but this regime is often inaccessible in emerging devices that suffer from high contact resistance or early gate dielectric breakdown. Here, we propose a method of extracting mobility in transistors with gate-dependent contact resistance that does not require operation at high |$V_\mathrm{gs}$|, enabling accurate mobility extraction even in emerging transistors with strong contact gating. Our approach relies on updating the transfer length method (TLM) and can achieve <10% error even in regimes where conventional techniques overestimate mobility by >2$\times$.