Myeong Sook Oh

Role of ZrO2 incorporation in the suppression of negative bias illumination- induced instability in Zn-Sn-O thin film transistors

Thin film transistors (TFTs) with In and Ga-free multicomponent Zn–Sn–Zr–O (ZTZO) channel layers were fabricated using the cosputtering approach. The incorporation of ZrO2 into the Zn–Sn–O (ZTO) films increased the contact resistance, which led to the degradation of the transport properties. In contrast, the threshold voltage shift under negative bias illumination stress (NBIS) was largely improved from −12.5 V (ZTO device) to −4.2 V (ZTZO device). This improvement was attributed to the reduction in the oxygen vacancy defects in the ZTZO film, suggesting that the photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability.

Anomalous behavior of negative bias illumination stress instability in an indium zinc oxide transistor: A cation combinatorial approach

This study examined the effects of the indium fraction in indium zinc oxide (IZO) on the performance and stability of IZO thin film transistors (TFTs). The field-effect mobility and sub-threshold swing were much improved with increasing In fraction; 41.0 cm2/Vs and 0.2 V/decade, respectively, at 85 at. % In, compared to 1.1 cm2/Vs and 2.4 V/decade of ZnO TFTs. In contrast, a local minimum negative bias illumination stress instability was observed near 73–77 at. % In. This behavior was explained by a poly-crystalline to amorphous phase transition in IZO thin films.

Improvement of electrical and optical properties of molybdenum oxide thin films by ultralow pressure sputtering method

In this work, we investigated the structural, electrical and optical properties of molybdenum oxide thin films deposited by the reactive dc magnetron sputtering method. The molybdenum oxide films were prepared at sputtering pressures ranging from 6.7 × 10−1 to 6.7 × 10−2 Pa. In order to promote their electrical conductivity, all the deposited MoOx films were annealed in Ar ambient at 450 °C for 8 h. The resistivity of the MoOx films varied from 10−4 to 10−2 Ω cm depending on the O2 content in the sputtering ambient. The lowering of the resistivity of the MoO2 films was mainly attributed to the formation of a monoclinic MoO2 polycrystalline phase. As the sputtering pressure decreased, the content of monoclinic polycrystalline MoO2 phase increased, resulting in low resistivity films. The formation of the dominant MoO2 phase at lower sputtering pressures was attributed to the stress induced crystallization. The post-deposition annealed (PDA) MoOx film, deposited at an ultralow sputtering pressure (6.7 × 10−2 Pa) and O2 content of 40%, had an atomic ratio of O to Mo ≈ 2.85 and was highly transparent and conductive: the transmittance in the visible wavelength range of 400–500 nm was about 73% and the resistivity was 1.05 × 10−3 Ω cm. This result is superior to those of MoOx films epitaxially grown by the pulse laser deposition method.In this work, we investigated the structural, electrical and optical properties of molybdenum oxide thin films deposited by the reactive dc magnetron sputtering method. The molybdenum oxide films were prepared at sputtering pressures ranging from 6.7 × 10−1 to 6.7 × 10−2 Pa. In order to promote their electrical conductivity, all the deposited MoOx films were annealed in Ar ambient at 450 °C for 8 h. The resistivity of the MoOx films varied from 10−4 to 10−2 Ω cm depending on the O2 content in the sputtering ambient. The lowering of the resistivity of the MoO2 films was mainly attributed to the formation of a monoclinic MoO2 polycrystalline phase. As the sputtering pressure decreased, the content of monoclinic polycrystalline MoO2 phase increased, resulting in low resistivity films. The formation of the dominant MoO2 phase at lower sputtering pressures was attributed to the stress induced crystallization. The post-deposition annealed (PDA) MoOx film, deposited at an ultralow sputtering pressure (6.7 × 10−2...

Effects of thermally oxidized-SiN gate oxide on 4H-SiC substrate

We have investigated and reported the results on oxidized-SiN gate oxides on n-type 4H-SiC. The quality of this oxide has been compared with thermal nitrided and dry oxides. In the oxidized-SiC sample, a significant improvement in oxide deposition/growth rate has been obtained while the metal-oxide-semiconductor characteristics of the oxide are comparable to the thermal-nitrided oxide and much better than dry oxide. This achievement has been explained using a proposed chemical model.

Improvement in the performance of ZnO thin film transistors by using ultralow-pressure sputtering

Thin film transistors (TFTs) were fabricated with a zinc oxide (ZnO) channel deposited by ultralow-pressure sputtering (ULPS) at a pressure less than 1.3×10−3 Pa. The field-effect mobility (μFE) and the subthreshold gate swing (SS) of the ULPS-ZnO TFTs were dramatically improved up to 8.5 cm2/V s and 0.31 V/decade, respectively, compared to 1.6 cm2/V s and 1.31 V/decade for the ZnO TFTs fabricated by a conventional sputtering pressure (CSP) of 6.7×10−1 Pa. The improved characteristics of the ULPS-ZnO TFTs compared to the CSP-ZnO one can be attributed to the greater densification of the ZnO semiconductor film at the lower deposition pressure.

Effect of Post-Oxidation Annealing on High-Temperature Grown SiO2/4H-SiC Interface

We have investigated the electrical and physical properties of high-temperature (1300, 1400 oC) grown dry oxide with or without post oxidation annealing (POA) in nitric oxide (NO) gas. A significant reduction in interface-trap density (Dit) has been observed in 1300 oC-grown dry oxide with or without NO POA if compared with the Dit of 1400 oC-grown dry oxide. The reason for this has been explained in this paper.

Homoepitaxial growth of 4H-SiC by hot-wall CVD using BTMSM

Homoepitaxial growth of 4H-SiC epilayer by hot-wall chemical vapor deposition using bis-trimethylsilylmethane (BTMSM, C7H20Si2) precursor was investigated. The growth rate of 4H-SiC was investigated as a function of the growth temperature and source flow rate. The FWHM values of epilayers as the growth temperature and source flow rate also investigated. The growth rate of 4H-SiC epilayer grown by hot-wall CVD was 3.0 μm/h and the background doping level of 4H-SiC epilayer was mid 1015/cm3.

Schottky Barrier Diode Fabricated by MOCVD-Grown Epilayer Using Bis-Trimethylsilylmethane Precursor

Schottky barrier diode (SBD) was fabricated by MOCVD using bistrimethylsilylmethane (BTMSM, C7H20Si2) precursor. The 4H-SiC substrates which had different crystallographic characteristics were used for the comparison of the crystallinity effect on the electrical properties of the SBDs. From the measurement of the reverse I-V characteristics of the SBDs with micropipes, it is shown that the origin of the main leakage path and early breakdown (or ohmic behavior in reverse bias) in 4H-SiC SBDs is the grain boundaries caused by the inclusions or other defects. The best performance of SBD were shown in the epilayer grown at 1440 oC using high quality substrate, and the breakdown voltage and reverse leakage current were about 450 V and 10-9 A/cm2, respectively.

Fabrication of 4H-SiC Schottky barrier diodes with the epilayer grown by Bis-trimethylsilylmethane precursor

The authors fabricated the 4H-SiC Schottky barrier diodes (SBDs) with the epilayers grown using the MOCVD. Bis-trimethylsilylmethane (BTMSM, [C₇H₂₀Si₂]) was used as a single precursor for Si and C sources.