Dimension Scaling Effects on Conduction and Low Frequency Noise Characteristics of ITO-Stabilized ZnO Thin Film Transistors

Yuan Liu,Man Wong,Sunbin Deng,Yu-Xuan Huang,Rongsheng Chen,Hoi-Sing Kwok

doi:10.1109/jeds.2020.2986231

Abstract

Conduction characteristics and low frequency noises in ITO-stabilized ZnO thin film transistors (TFTs) with constant channel width (W=50 μm) and different channel lengths (L=5, 10, 25, 50 and 100 μm) are measured and analysis. Firstly, dependences of threshold voltage and field effect mobility on channel length are examined. With decreasing channel length, the threshold voltage shifts to the negative direction which may attribute to carrier diffusion from source/drain to the intrinsic device channel. In addition, significant degradation of field effect mobility is observed in short channel device which are induced by the presence of series contact resistance. The value of contact resistance has also been extracted. Secondly, the drain current noise power spectral densities (S ID ) are measured at varied effective gate voltages. The measured noises follow a 1/f γ and y is about -1.1. Moreover, the normalized noises (S ID /I ds ) are dependent linearly on the inverse of channel length and the slope is about -0.75. Finally, the dominant mechanism of low frequency noise in ITO-stabilized ZnO thin film transistor are examined. The slope of normalized noise against effective gate voltage are extracted, which are varied from -1.03 to -1.84 with decreasing channel length and thus it indicates that ITO-stabilized ZnO TFTs varied from bulk dominated devices to interface dominated devices. By using of ΔN-Δμ model, the normalized noises are simulated by considering of contact resistance. Several noise parameters (flat-band voltage noise spectral density, etc) are extracted and analysis.

Highlights

As switching elements for addressing the pixel circuit [1], Sn-doped indium-zinc-oxide (IZO) thin-film transistors (TFTs) exhibit high mobility and low off current [1], [2], which can meet the requirements of generation high vision with a pixel resolution of 8k×4k and a lower charged time per unit frame [3], [4]
ITO-stabilized ZnO TFTs varied from bulk dominated devices to interface dominated devices with the decrement of channel length, and it may result to the variation of the slope of SI/Id2 against Vgs − Vth
The slopes of SID/Id2s against Vgs −Vth of our devices are between −1 and −2, Low frequency noise (LFN) can be simulated by using carrier number with correlated mobility fluctuations ( N- μ) model [28]–[30]

Summary

INTRODUCTION

As switching elements for addressing the pixel circuit [1], Sn-doped indium-zinc-oxide (IZO) thin-film transistors (TFTs) exhibit high mobility (even over 50 cm2/Vs) and low off current (less than 10−13 A) [1], [2], which can meet the requirements of generation high vision with a pixel resolution of 8k×4k and a lower charged time per unit frame (less than 1.2 μs) [3], [4]. ITO-stabilized ZnO TFTs varied from bulk dominated devices to interface dominated devices with the decrement of channel length, and it may result to the variation of the slope of SI/Id2 against Vgs − Vth. As discussed above, the slopes of SID/Id2s against Vgs −Vth of our devices are between −1 and −2, LFN can be simulated by using carrier number with correlated mobility fluctuations ( N- μ) model [28]–[30]. By consider of contact resistance, the noise can be expressed by [12], [23], [32]

Ids Vds

CONCLUSION