• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.4
• /
• pp.272-275
• /
• 2019

We investigated the electrical characteristics of amorphous silicon-zinc-tin-oxide (a-SZTO) thin films deposited by RF-magnetron sputtering at room temperature depending on the deposition time. We fabricated a thin film transistor (TFT) with a bottom gate structure and various channel thicknesses. With increasing channel thickness, the threshold voltage shifted negatively from -0.44 V to -2.18 V, the on current ($I_{on}$) and field effect mobility (${\mu}_{FE}$) increased because of increasing carrier concentration. The a-SZTO film was fabricated and analyzed in terms of the contact resistance and channel resistance. In this study, the transmission line method (TLM) was adopted and investigated. With increasing channel thickness, the contact resistance and sheet resistance both decreased.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.256-256
• /
• 2012

Oxide semiconductors such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO) have attracted a lot of research interest owing to their high potential for application as thin film transistors (TFTs) [1,2]. However, the instability of oxide TFTs remains as an obstacle to overcome for practical applications to electronic devices. Several studies have reported that the electrical characteristics of ZnO-based transistors are very sensitive to oxygen, hydrogen, and water [3,4,5]. To improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistor, back channel passivation layer is essential for the long term bias stability. In this study, we investigated the instability of amorphous indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) by the back channel contaminations. The effect of back channel contaminations (humidity or oxygen) on oxide transistor is of importance because it might affect the transistor performance. To remove this environmental condition, we performed vacuum seasoning before the deposition of hybrid passivation layer and acquired improved stability. It was found that vacuum seasoning can remove the back channel contamination if a-IGZO film. Therefore, to achieve highly stable oxide TFTs we suggest that adsorbed chemical gas molecules have to be eliminated from the back-channel prior to forming the passivation layers.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.3
• /
• pp.143-145
• /
• 2016

In order to find suitable source and drain (S/D) electrodes for amorphous InGaZnO thin film transistors (a-IGZO TFTs), the specific contact resistance of interface between the channel layers and various S/D electrodes, such as Ti/Au, a-IZO and multilayer of a-IGZO/Ag/a-IGZO, was investigated using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes had good performance and low contact resistance due to the homo-junction with channel layer. The stability was measured with different electrodes by a positive bias stress test. The result shows the a-IGZO TFTs with a-IGZO/Ag/a-IGZO electrodes were more stable than other devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.2
• /
• pp.71-75
• /
• 2014

To observe the optical characteristic of oxide semiconductor depending on the degree of bonding structures, SiOC, ZnO and IGZO were prepared by the RF magnetron sputter system and chemical vapor deposition. Generally, crystal ZnO, amorphous SiOC and IGZO changed the optical characteristics in according to the electro-chemical behavior due to the oxygen vacancy at an interface between different groups. Transmittance of SiOC and IGZO with amorphous structures was higher than that of ZnO with crystal structure, because of lowering the carrier concentration due to the recombination of electron and holes carriers as oxygen vacancies. Besides, the energy gap of amorphous SiOC and IGZO was higher than the energy gap of crystal ZnO. The diffusion mobility of holes is higher than the drift mobility of electrons.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1586-1589
• /
• 2009

We investigated the influence of chemical compositions of gallium and indium cations on the performance of solgel derived amorphous gallium indium zinc oxide (a-GIZO) based thin-film transistors (TFTs). Systematical composition study allows us to understand the solutionprocessed a-GIZO TFTs. Understanding of the compositional influence can be utilized for tailoring the solution processed amorphous oxide TFTs for the specific applications.

• Korean Journal of Materials Research
• /
• v.1 no.3
• /
• pp.125-131
• /
• 1991

Boron penetration phenomenon of $p^{+}$ silicon gate with as-deposited amorphous or polycrystalline Si upon high temperature annealing was investigated using high frequency C-V (Capacitance-Volt-age) analysis, CCST(Constant Current Stress Test), TEM(Transmission Electron Microscopy) and SIMS(Secondary Ion Mass Spectroscopy), C-V analysis showed that an as-deposited amorphous Si gate resulted in smaller positive shifts in flatband voltage compared wish a polycrystalline Si gate, thus giving 60-80 percent higher charge-to-breakdown of gate oxides. The reduced boron penetration of amorphous Si gate may be attributed to the fewer grain boundaries available for boron diffusion into the gate oxide and the shallower projected range of $BF_2$ implantation. The relation between electron trapping rate and flatband voltage shift was also discussed.

• Transactions on Electrical and Electronic Materials
• /
• v.16 no.3
• /
• pp.139-141
• /
• 2015

Contact resistance of interface between the channel layers and various S/D electrodes was investigated by transmission line method. Different electrodes such as Ti/Au, a-IZO, and multilayer of a-IGZO/Ag/a-IGZO were compared in terms of contact resistance, using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes showed good performance and low contact resistance due to the homo-junction with channel layer.

• 전기의세계
• /
• v.29 no.2
• /
• pp.111-117
• /
• 1980

Contacts formed by vacuum evaporation of As-Te-Si-Ge chalcogenide glass onto Al metal (99.9999%) are studied by measuring paralle capacitance C(V), Cp(w), resistance R(V), Rp(w), and I-V characteristics. The fact that contact metal alloying produced high-resistance region is confirmed from the measurements of parallel capacitance and resistance. From the I-V characteristics in the pre-switcing region, it is found that electronic conduction and sitching occurs in the vicinity of metal-amorphous semiconductor interface. From the experimental obsevations, it is concuded that the current flow in the thin film is space-charge limited current (SCLC) due to the tunneling of electrons through the energy barriers.

• Journal of the Semiconductor & Display Technology
• /
• v.11 no.4
• /
• pp.19-23
• /
• 2012

We report microbolometer characteristic with n-type and p-type amorphous silicon thin film. The n-type and p-type amorphous silicon thin films were made by PECVD. The electrical properties of n-type and p-type a-Si:H thin films were investigated as a function of doping gas flow rate. The doping gas used $B_2H_6/Ar$ (1:9) and $PH_3/Ar$ (1:9). In general, the conductivity of doping a-Si:H thin films increased as doping gas increase but the conductivity of a-Si:H thin films decreased as the doping gas increase because doping gas concentration increase led to dilution gas (Ar) increase as the same time. We fabricated an amorphous silicon microbolometer using surface micromachining technology. The fabricated microbolometer had a negative TCR of 2.3%. The p-type microbolometer had responsivity of $5{\times}10^4V/W$ and high detectivity of $3{\times}10^8cm(Hz)^{1/2}/W$. The p-type microbolometer had more detectivity than n-type for less noise value.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.210-213
• /
• 2004

The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. Memory switching in chalcogenides is mostly a thermal process, which involves phase transformation from amorphous to crystalline state. The nonvolatile memory cells are composed of a simple sandwich (metal/chalcogenide/metal). It was formed that the threshold voltage depends on thickness, electrode distance, annealing time and temperature, respectively.