Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses.

Dapeng Wang,Hua Li,Mamoru Furuta,Wenjing Zhao

doi:10.3390/ma11040559

Dapeng Wang, Hua Li + Show 2 more

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In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses (TIGZO) are investigated. As the TIGZO increased, the turn-on voltage (Von) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm2·V−1·s−1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the TIGZO. The PBS results exhibit that the Von shift is aggravated as the TIGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various TIGZO values is revealed using current–voltage and capacitance–voltage (C–V) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source (Cgs) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the TIGZO value increased, the hump in the off state of the Cgs curve was gradually weakened.

Highlights

Amorphous indium gallium zinc oxide (a-IGZO), as a representative of an amorphous metal oxide-based semiconductor, has been widely investigated for use in the active layer of thin-film transistors (TFTs) due to its high electron mobility, good transparency in visible light, chemical and thermal stability, low temperature processing, and smooth surface [1,2,3,4]
It is found that the ∆V on under positive gate bias stress (PBS) is aggravated as the decrease in the TIGZO, which is due to the enhancement of the vertical electrical field in the channel
The drain current stress (DCS)-induced instability in the amorphous indium gallium zinc oxide (a-IGZO) TFTs with various TIGZO values is revealed by the combination of I–V and

Summary

Introduction

Amorphous indium gallium zinc oxide (a-IGZO), as a representative of an amorphous metal oxide-based semiconductor, has been widely investigated for use in the active layer of thin-film transistors (TFTs) due to its high electron mobility, good transparency in visible light, chemical and thermal stability, low temperature processing, and smooth surface [1,2,3,4]. Valdinoci et al [13] have reported that the electron-hole pair generation by impact ionization near the drain region caused the floating body effect in high μ poly-Si TFTs. the electrical stability under drain current stress was considered to be an important issue, especially for high-μ oxide TFTs. the active layer thickness is an important parameter to adjust device electrical properties, such as on/off ratio, threshold voltage, and field effect mobility [14,15,16]. The impact of the active layer thickness (TIGZO ) on the instability induced by the positive gate bias stress (PBS) and the drain current stress (DCS) in a-IGZO TFTs should be well investigated. The DCS-induced instability in the a-IGZO TFTs with various TIGZO is revealed by the combination of current-voltage (I–V) and capacitance-voltage (C–V) measurements

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