Monthly Archives: October 2014

Large periphery AlInN/AlN/GaN metal-oxide-semiconductor heterostructure field-effect transistors on sapphire substrate

We report on the study of multi-gate AlInN/InN/GaN metal-oxide semiconductor field-effect transistors (MOSHFET) over a sapphire substrate with gate widths varying from 0.25 mm–5 mm. A high saturation output current of ∼1.3 A and a maximum extrinsic transconductance of 210 mS are demonstrated for the 5 mm wide device with a gate length of 1.8 μ m and a source-drain spacing of 12 μ m. The maximum saturation output current and the maximum extrinsic transconductance appear to scale nearly linearly with the gate width up to 1 mm, beyond which joule heating dominates. These results show the potential of these MOSHFETs for high-voltage and high power operation.

Large object investigation by digital holography with effective spectrum multiplexing under single-exposure approach

We present a method to investigate large object by digital holography with effective spectrum multiplexing under single-exposure approach. This method splits the original reference beam and redirects one of its branches as a second object beam. Through the modified Mach-Zehnder interferometer, the two object beams can illuminate different parts of the large object and create a spectrum multiplexed hologram onto the focal plane array of the charge-coupled device/complementary metal oxide semiconductor camera. After correct spectrum extraction and image reconstruction, the large object can be fully observed within only one single snap-shot. The flexibility and great performance make our method a very attractive and promising technique for large object investigation under common 632.8 nm illumination.

Electron-transporting phenazinothiadiazoles with engineered microstructure

J. Mater. Chem. C, 2014, Advance ArticleDOI: 10.1039/C4TC01992J, PaperBenjamin D. Lindner, Fabian Paulus, Anthony L. Appleton, Manuel Schaffroth, Jens U. Engelhart, Korwin M. Schelkle, Olena Tverskoy, Frank Rominger, Manuel Hamburger, Uwe H. F. BunzNovel phenazinothiadiazoles were prepared by condensation of ortho-quinones and an alkynylated 5,6-diamino-2,1,3-4 benzothiadiazole and evaluated as transport materials in thin film transistors.To cite this article before page numbers are assigned, use the DOI form of citation above.The content of this RSS Feed (c) The Royal Society of Chemistry

Fabrication and characterization of Cu(In,Ga)Se 2 p-channel thin film transistors

Cu(In,Ga)Se2 thin film transistors are demonstrated with the on-off ratio of ∼103 and the saturation hole mobility of 1.8 cm2/V-s. Due to the high hole concentration (∼5 × 1017 cm−3), the channel needs to be etched to turn off for the accumulation mode operation. The Cu(In,Ga)Se2 film after etching reveals a larger mobility, and a narrower (112) X-ray diffraction line than the original thick layer, indicating the better crystallinity of the initial growth as compared to the subsequent Cu(In,Ga)Se2 layer. Both the hole concentration and the saturation mobility increase with the decreasing Cu/(In + Ga) ratio probably due to the effect of Cu vacancies.

Printable sensors for explosive detonation

Here, we report the development of an organic thin film transistor (OTFT) based on printable solution processed polymers and employing a quantum tunnelling composite material as a sensor to convert the pressure wave output from detonation transmission tubing (shock tube) into an inherently amplified electronic signal for explosives initiation. The organic electronic detector allows detection of the signal in a low voltage operating range, an essential feature for sites employing live ordinances that is not provided by conventional electronic devices. We show that a 30-fold change in detector response is possible using the presented detector assembly. Degradation of the OTFT response with both time and repeated voltage scans was characterised, and device lifetime is shown to be consistent with the requirements for on-site printing and usage. The integration of a low cost organic electronic detector with inexpensive shock tube transmission fuse presents attractive avenues for the development of cheap and simple assemblies for precisely timed initiation of explosive chains.

Investigation of temperature-dependent asymmetric degradation behavior induced by hot carrier effect in oxygen ambiance in In–Ga–Zn-O thin film transistors

Publication date: Available online 5 October 2014 Source:Thin Solid Films Author(s): Bo-Wei Chen , Ting-Chang Chang , Yu-Ju Hung , Tien-Yu Hsieh , Ming-Yen Tsai , Po-Yung Liao , Wu-Wei Tsai , Wen-Jen Chiang The effects of oxygen ambiance on electrical characteristic degradation phenomena in a-InGaZnO thin film transistor with different biases and temperatures are investigated. It can be found that oxygen is substantially adsorbed on the backchannel and results in device instabilities during positive gate bias stress. However, visible light irradiation is found to desorb the adsorbed oxygen ions and this verifies that oxygen dominates the degradation behavior. Moreover, comparing with that in vacuum, hot-carrier stress in oxygen ambiance leads to an extra potential barrier height near the drain side due to oxygen adsorption and causes asymmetric degradation. Furthermore, the asymmetric degradation behavior after hot-carrier stress in oxygen ambiance is suppressed at high temperature due to temperature-induced oxygen desorption or heat-induced holes injecting into the gate insulator.

A study on the influence of local doping in atomic layer deposited Al:ZnO thin film transistors

J. Mater. Chem. C, 2014, Advance ArticleDOI: 10.1039/C4TC01727G, PaperYoon Jang Chung, Won Jin Choi, Seong Gu Kang, Chang Wan Lee, Jeong-O Lee, Ki-Jeong Kong, Young Kuk LeeDoping positions can be as important as dopant materials and concentrations in designing optimal thin film transistors.To cite this article before page numbers are assigned, use the DOI form of citation above.The content of this RSS Feed (c) The Royal Society of Chemistry

Anomalous degradation behaviors under illuminated gate bias stress in a-Si:H thin film transistor

Publication date: Available online 2 October 2014 Source:Thin Solid Films Author(s): Ming-Yen Tsai , Ting-Chang Chang , Ann-Kuo Chu , Tien-Yu Hsieh , Kun-Yao Lin , Yi-Chun Wu , Shih-Feng Huang , Cheng-Lung Chiang , Po-Lin Chen , Tzu-Chieh Lai , Chang-Cheng Lo , A. Lien This study investigates the impact of gate bias stress with and without light illumination in a-Si:H thin film transistors. It has been observed that the I-V curve shifts toward the positive direction after negative and positive gate bias stress due to interface state creation at the gate dielectric. However, this study found that threshold voltages shift negatively and that the transconductance curve maxima are anomalously degraded under illuminated positive gate bias stress. In addition, threshold voltages shift positively under illuminated negative gate bias stress. These degradation behaviors can be ascribed to charge trapping in the passivation layer dominating degradation instability and are verified by a double gate a-Si:H device.

Photoelectron spectroscopy study of thin Ag films deposited on to amorphous In–Ga–Zn–O surface

Publication date: 3 November 2014 Source:Thin Solid Films, Volume 570, Part A Author(s): Se Jun Kang , Jaeyoon Baik , Taekyun Ha , Chong Do Park , Hyun-Joon Shin , JaeGwan Chung , Jaecheol Lee Ag was thermally evaporated onto amorphous In–Ga–Zn–O (a-IGZO) thin film, and the Ag-thickness (<0.3nm)-dependent chemical states of the Ag-deposited a-IGZO thin-film surfaces were investigated by high-resolution X-ray photoelectron spectroscopy. As Ag layer thickness increased, Ag 3d shifted towards the lower binding energy (BE) side and In 3d developed a lower-BE component; however, O 1s, Ga 3d, and Zn 3d showed much smaller spectral feature changes than Ag 3d or In 3d. The analysis suggests that Ag atoms preferentially interact and share electrons with In atoms. The Ag 4d split feature at the valence band and the metallic states near the Fermi edge were noticeably visible when the Ag thickness was greater than 0.1nm.

Significant roles of low-temperature post-metallization annealing in solution-processed oxide thin-film transistors

Inspired by the silicide technology in manufacturing silicon devices and the ongoing lack of knowledge on post-metallization annealing in realizing oxide devices, we investigated post-contact annealing for solution-processed InGaZnO transistors. Low-temperature annealing in air is found to significantly improve device uniformity, reproducibility, and subthreshold charge transport. However, this method is highly dependent on the employed contact metal. Detailed examination of devices using Al, Au, and Cu reveals that the physics of a metal/semiconductor interface is vital to its post-anneal response, which results in distinct device characteristics. Our results provide clues to better understand oxide transistors and to optimize their performance.