Modeling and characterization of metal-semiconductor-metal-based source-drain contacts in amorphous InGaZnO thin film transistors

Abstract

Due to the inherent property of large contact and parasitic resistances in amorphous InGaZnO (a-IGZO) thin film transistors (TFTs), a metal-semiconductor-metal (MSM) structure is a key element in a-IGZO TFTs. Therefore, voltage drops across resistances and MSM structure should be fully considered in the modeling and characterization of a-IGZO TFTs. A physics-based semiempirical model for the current-voltage characteristics of the MSM structure for the source-channel-drain contact in a-IGZO TFTs is proposed and verified with experimental results. The proposed model for the current in a-IGZO MSM structures includes a thermionic field emission [JTFE∝exp(VR,Schottky/Vo)] and trap-assisted generation (Jgen∝VR,Schottky) in addition to the thermionic emission current (JS: Independent of the bias) under reverse bias. Experimental result suggests that electrical characteristics of the MSM structure depend not only on the Schottky barrier but also on the bulk property of the a-IGZO active layer.

Reduction of Photo-Leakage Current in ZnO Thin-Film Transistors With Dual-Gate Structure

“…Together with further experimental and simulation studies [15], [16], we proposed that the phenomena under light-irradiation was closely related to the Schottky contact properties of source and that photoleakage current was attributed to the reduction of potential barrier width at the source Schottky contacts that is in proximity to the source/channel interface associated with accumulation of photo-generated holes at the interface region. In the case of amorphous InGaZnO TFTs, the electrical properties under dark conditions are modeled by Schottky contacts between metal electrodes and channel layer [17]. This supports the validity of our proposed model since the properties of ZnO are similar to those of InGaZnO.…”

Conduction instability of amorphous InGaZnO thin-film transistors under constant drain current stress

“…4 can be linearly fitted to the trapassisted thermal generation current (J gen ) versus Schottky diode reverse bias (V R,Schottky ), which has the relationship of the Eq. (6) as discussed in [16]:…”

Effects of an Aluminum Contact on the Carrier Mobility and Threshold Voltage of Zinc Tin Oxide Transparent Thin Film Transistors

“…The trap-assisted thermal generation current I GE is proportional to (1 + V R /V bi ) 1/2 [23], where V R and V bi are the voltage drop across the Schottky barrier and the built-in potential of the Schottky contact, respectively. The field emission current and thermionic field emission current are known to be exponentially proportional to V R such that I FE ∝ V R 2 exp(-K 1 /qV R ) [24] and I TFE ∝ exp(qV R /K 2 ) [25], where K 1 and K 2 are the characteristic energies of the field emission current and thermionic field emission current, respectively. The drainsource voltage V DS is divided between the two Schottky contacts and the channel.…”

“…If the Al-ZTO contact is a rectifying contact, either the source-channel junction or the channel-drain junction will be reverse biased. Electrons are transported across a metalsemiconductor junction under reverse bias in the following ways [23][24][25]: thermal generation (I GE ) in a space charge layer, field emission (I FE ) or thermionic field emission (I TFE ) through the potential barrier, and thermionic emission (I TE ) over the potential barrier.…”