Yunyong Nam

Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors.

Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current-voltage and transient current-time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm(2) v(-1) s(-1)), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability.

Space charge-induced unusually-high mobility of a solution-processed indium oxide thin film transistor with an ethylene glycol incorporated aluminum oxide gate dielectric

The incorporation of ethylene glycol (EG) into a high-k aluminium oxide gate dielectric layer was achieved by a solution process, leading to a distinct increase in the mobility of indium oxide TFT. Frequency-dependent capacitance originating from residual EG was examined and the accompanying effects on indium oxide TFT were studied.

Improvement of bias stability of oxyanion-incorporated aqueous sol–gel processed indium zinc oxide TFTs

Oxyanion-incorporated indium zinc oxide (IZO) TFTs exhibiting excellent bias stabilities are fabricated from aqueous IZO precursor solutions blended with a catalytic amount of inorganic acids (H2SO4, H3PO4, H3BO3). The resulting oxyanion-incorporated IZO TFTs (SO–IZO, PO–IZO, BO–IZO) exhibit improved bias stabilities under NBS, PBS, NBTS, and PBTS conditions.

Beneficial effect of hydrogen in aluminum oxide deposited through the atomic layer deposition method on the electrical properties of an indium–gallium–zinc oxide thin-film transistor

ABSTRACT Described herein is the role of hydrogen in aluminum oxide (Al2O3) gate dielectrics in amorphous indium–gallium–zinc oxide (a-InGaZnO or a-IGZO) thin-film transistors (TFTs). Compared to a-IGZO TFTs with a low-temperature (150°C) Al2O3 gate dielectric, a-IGZO devices with a high-temperature (250–300°C) Al2O3 gate dielectric exhibit poor transistor characteristics, such as low mobility, a high subthreshold slope, and huge hysteresis. Through DC and short-pulsed current–voltage (I–V) measurements, it was revealed that the degradation of the transistor performance stems from the charging and discharging phenomenon at the interface traps located in the interface between the a-IGZO semiconductor and the Al2O3 gate insulator. It was found that the low-temperature Al2O3 atomic layer deposition processed film contains a higher density of hydrogen atoms compared to high-deposition-temperature films. The study results show that a high concentration of hydrogen atoms can passivate the defect sites in the interface and bulk, which produces excellent transistor characteristics. This study demonstrated that hydrogen has a beneficial effect on the defect passivation for oxide TFTs.

The Influence of Hydrogen on Defects of In–Ga–Zn–O Semiconductor Thin-Film Transistors With Atomic-Layer Deposition of Al 2 O 3

Hydrogen plays a crucial role in several oxide semiconductors, where the amount of hydrogen significantly influences the device performance. Thus, its manipulation in oxide semiconductors is important for device performance. In our investigation, we studied the effect of hydrogen on defects in In-Ga-Zn-O semiconductor thin-film transistors (TFTs), as it varies with Al2O3 atomic layer deposition temperature. We found that the total trap-density (Ntot) extracted by the sub-threshold slope and the trap density (Nt) measured by low-frequency noise (LFN) as well as the density-of-states analyzed by capacitance-voltage decreased with increasing amounts of hydrogen in the oxide semiconductor. Given that LFN data show that mobility fluctuation is the major origins of noise and the front channel of TFT is a major carrier transport region, our results indicate that hydrogen effectively passivates the defects in front channel of oxide semiconductor and contributes to achieving superior device performance.

Effect of hydrogen diffusion in an In–Ga–Zn–O thin film transistor with an aluminum oxide gate insulator on its electrical properties

We fabricated amorphous InGaZnO thin film transistors (a-IGZO TFTs) with aluminum oxide (Al2O3) as a gate insulator grown through atomic layer deposition (ALD) method at different deposition temperatures (Tdep). The Al2O3 gate insulator with a low Tdep exhibited a high amount of hydrogen in the film, and the relationship between the hydrogen content and the electrical properties of the TFTs was investigated. The device with the Al2O3 gate insulator having a high H content showed much better transfer parameters and reliabilities than the low H sample. This is attributed to the defect passivation effect of H in the active layer, which is diffused from the Al2O3 layer. In addition, according to the post-annealing temperature (Tpost-ann), a-IGZO TFTs exhibited two unique changes of properties; the degradation in low Tpost-ann and the enhancement in high Tpost-ann, as explained in terms of H diffusion from the gate insulator to an active layer.