Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature

Abstract

The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal-OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm(2) V(-1) sec(-1), the carrier concentration at ∼10(20) cm(-3) without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.

The self-activated radical doping effects on the catalyzed surface of amorphous metal oxide films

“…These findings appear to demonstrate the reasons for the improved stability results by the decrease in V 0 and reduced V 0 layer effect, which is similar to the self-passivation effect, at the back-channel surface region 29 . Additionally, to investigate the OH* bond with metal cation, we analyzed Zn 2p3/2 XPS spectra because Zn atoms can react well with oxygen species compared to In and Ga, due to their lower bond energy 30 . As a result, Fig.…”

Orders-of-magnitude enhancement in conductivity tuning in InGaZnO thin-film transistors via SiNx passivation and dual-gate modulation

“…The experiment results suggest that the enhanced conductivity tuning and stability can be attributed to a combination of the moderate hydrogen diffusion from the SiN x passivation layer towards the IGZO layer and the formation of stable ionic configurations [12] during the thermal annealing. The elemental depth profiles confirm the presence of H in the treated IGZO films, but the incorporation of hydrogen simultaneously creates excess free electrons, resulting in the negative shifting of the transfer curves and the degradation of the subthreshold properties [8][9][10]. To overcome this issue, an additional gate (Mo) was deposited on the top of the passivation layer, enabling the dual-gate modulation of the channel carriers and reducing the subthreshold swing from the pristine value of 2.6-1.2 V/dec while the top gate was set to −4 V. Consequently, hydrogendoped IGZO TFTs exhibiting an on-current 30 times higher than that of the regular IGZO TFTs alongside suppressed degradation of the subthreshold properties were obtained.…”

“…carbon nanotube [4], nanowire [5,6]), although this strategy is not currently suitable for the manufacture of large-area devices. Another approach for enhancing the conductivity of AOS is the introduction of hydrogen, which is usually achieved via gas control film deposition [7], device annealing under a high-pressure H 2 atmosphere [8], hydrogen plasma treatment [9], ultraviolet light exposure [10], etc. These methods, however, either metallize the oxide semiconductor [7,10,11] or slightly affect the conductivity [7][8][9].…”

“…Another approach for enhancing the conductivity of AOS is the introduction of hydrogen, which is usually achieved via gas control film deposition [7], device annealing under a high-pressure H 2 atmosphere [8], hydrogen plasma treatment [9], ultraviolet light exposure [10], etc. These methods, however, either metallize the oxide semiconductor [7,10,11] or slightly affect the conductivity [7][8][9]. Described in this work is the fabrication of hydrogendoped long-channel IGZO TFTs (hereinafter referred to as 'IGZO:H') with greatly improved transfer performance via the simple plasma-enhanced chemical vapor deposition (PECVD) technique.…”

Stability Behavior of Self-Aligned Coplanar a-IGZO Thin Film Transistors Fabricated by Deep Ultraviolet Irradiation

“…[14][15][16] The water molecule bond dissociation energy is known to be 497.1 kJ/mol or 5.1 eV. 17 The energies of DUV light of 185 and 254 nm wavelength are 6.7 and 4.9 eV, respectively.…”