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Jong-lam Lee - One of the best experts on this subject based on the ideXlab platform.
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Thermally stable SiC MESFET with iridium oxide gate electrode
Electronics Letters, 2004Co-Authors: S.y. Han, Jong-lam LeeAbstract:Thermally stable SiC MESFET using iridium-oxide (IrO 2 ) gate Contact has been demonstrated and compared with conventionally used Ni Schottky Contact. It was found that the IrO 2 Schottky Contact is thermally stable and no distinct change of device performances was observed even after annealing at 450°C for 15 h. This is because the IrO 2 suppressed the interdiffusion of the Contact metals into the SiC substrate. It is suggested that IrO 2 is a promising candidate as gate electrode for high-temperature SiC MESFETs.
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IrO2 Schottky Contact on n-type 4H-SiC
Applied Physics Letters, 2003Co-Authors: Sang Youn Han, Ho Won Jang, Jong-lam LeeAbstract:A thermally stable IrO2 Schottky Contact on n-type 4H-SiC was achieved by annealing an Ir Contact under O2 ambient. The IrO2 Contact exhibited a high Schottky barrier height of 2.22 eV and low reverse leakage current. Little degradation in Schottky barrier height was observed even after annealing at 450 °C for 24 h under atmospheric air. The oxidation annealing transformed the Ir layer into IrO2, resulting in the increase in the work function of the Contact layer. Simultaneously, Si atoms diffused out, leaving the Si vacancy below the Contact. These played a role in forming a thermally stable Schottky Contact with a high Schottky barrier height.
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thermally stable ir Schottky Contact on algan gan heterostructure
Applied Physics Letters, 2003Co-Authors: Chang Min Jeon, Ho Won Jang, Jong-lam LeeAbstract:We report thermally stable Ir Schottky Contacts on AlGaN/GaN heterostructure. The Schottky barrier height was increased from 0.68 to 1.07 eV, and the reverse leakage current dramatically decreased after annealing at 500 °C under O2 ambient. No degradation in Schottky barrier height was observed after annealing at 500 °C for 24 h. The oxidation annealing caused predominant Ga outdiffusion to the surface, leading to the shift of surface Fermi level to the energy level of Ga vacancy. This played a role in forming the Schottky Contact with large barrier height and excellent thermal stability.
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gan metal semiconductor metal ultraviolet photodetector with iro2 Schottky Contact
Applied Physics Letters, 2002Co-Authors: Jong Kyu Kim, Chang Min Jeon, Ho Won Jang, Jong-lam LeeAbstract:Iridium oxide (IrO2) was used as the Schottky barrier materials of GaN metal–semiconductor–metal (MSM) ultraviolet photodetector. Annealing an Ir Contact at 500 °C under O2 ambient, the reverse leakage current density at −5 V reduced by the four orders of magnitude, to ∼10−6 A/cm2. Simultaneously, Schottky barrier height and optical transmittance increased to 1.48 eV and 74.8% at 360 nm, respectively. The dramatic improvement originated from the formation of IrO2 by the annealing, resulting in the increase in the responsivity of the GaN MSM photodetector by one order of magnitude, in comparison with the photodetector with Pt Schottky Contact.
Zhong Lin Wang - One of the best experts on this subject based on the ideXlab platform.
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piezotronic effect enhanced Schottky Contact zno micro nanowire humidity sensors
Nano Research, 2014Co-Authors: Ranran Zhou, Lin Dong, Caofeng Pan, Zhong Lin WangAbstract:A ZnO micro/nanowire has been utilized to fabricate Schottky-Contacted humidity sensors based on a metal-semiconductor-metal (M-S-M) structure. By means of the piezotronic effect, the signal level, sensitivity and sensing resolution of the humidity sensor were significantly enhanced when applying an external strain. Since a higher Schottky barrier markedly reduces the signal level, while a lower Schottky barrier decreases the sensor sensitivity due to increased ohmic transport, a 0.22% compressive strain was found to optimize the performance of the humidity sensor, with the largest responsivity being 1,240%. The physical mechanism behind the observed mechanical-electrical behavior was carefully studied by using band structure diagrams. This work provides a promising way to significantly enhance the overall performance of a Schottky-Contact structured micro/nanowire sensor.
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supersensitive fast response nanowire sensors by using Schottky Contacts
Advanced Materials, 2010Co-Authors: Jun Zhou, Pinghung Yeh, Teyu Wei, Zhong Lin WangAbstract:A Schottky barrier can be formed at the interface between a metal electrode and a semiconductor. The current passing through the metal-semiconductor Contact is mainly controlled by the barrier height and barrier width. In conventional nanodevices, Schottky Contacts are usually avoided in order to enhance the contribution made by the nanowires or nanotubes to the detected signal. We present a key idea of using the Schottky Contact to achieve supersensitive and fast response nanowire-based nanosensors. We have illustrated this idea on several platforms: UV sensors, biosensors, and gas sensors. The gigantic enhancement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky Contact can be very beneficial to the sensitivity of nanosensors.
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Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor
Journal of the American Chemical Society, 2009Co-Authors: Teyu Wei, Pinghung Yeh, Zhong Lin WangAbstract:A new single nanowire based nanosensor is demonstrated for illustrating its ultrahigh sensitivity for gas sensing. The device is composed of a single ZnO nanowire mounted on Pt electrodes with one end in Ohmic Contact and the other end in Schottky Contact. The Schottky Contact functions as a "gate" that controls the current flowing through the entire system. By tuning the Schottky barrier height through the responsive variation of the surface chemisorbed gases and the amplification role played by the nanowire to Schottky barrier effect, an ultrahigh sensitivity of 32,000% was achieved using the Schottky Contacted device operated in reverse bias mode at 275 degrees C for detection of 400 ppm CO, which is 4 orders of magnitude higher than that obtained using an Ohmic Contact device under the same conditions. In addition, the response time and reset time have been shortened by a factor of 7. The methodology and principle illustrated in the paper present a new sensing mechanism that can be readily and extensively applied to other gas sensing systems.
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gigantic enhancement in response and reset time of zno uv nanosensor by utilizing Schottky Contact and surface functionalization
Applied Physics Letters, 2009Co-Authors: Jun Zhou, Wenjie Mai, Pinghung Yeh, Gang Bao, Ashok K Sood, D L Polla, Zhong Lin WangAbstract:UV response of ZnO nanowire nanosensor has been studied under ambient condition. By utilizing Schottky Contact instead of Ohmic Contact in device fabrication, the UV sensitivity of the nanosensor has been improved by four orders of magnitude, and the reset time has been drastically reduced from 417 to 0.8 s. By further surface functionalization with function polymers, the reset time has been reduced to 20 ms even without correcting the electronic response of the measurement system. These results demonstrate an effective approach for building high response and fast reset UV detectors. © 2009 American Institute of Physics. DOI: 10.1063/1.3133358 Ultraviolet UV photon detectors have a wide range of applications from environmental monitoring, missile launching detection, space research, high temperature flame detection to optical communications. 1 For these applications, fast response time, fast reset time, high selectivity, high responsivity, and good signal-to-noise ratio are commonly desired characteristics. 2 For UV photon detector based on polycrystalline ZnO thin film, a slow response time ranging from a few minutes to several hours is commonly observed. 3,4 Due
Pierre Berini - One of the best experts on this subject based on the ideXlab platform.
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surface plasmon Schottky Contact detector based on a symmetric metal stripe in silicon
Optics Letters, 2010Co-Authors: Christine Scales, Ian Breukelaar, Pierre BeriniAbstract:A Schottky Contact detector comprising a symmetric metal stripe buried in Si, capable of detecting surface plasmons at wavelengths below the bandgap of Si, is described. A model for the detector is proposed, and its performance is assessed at λ0=1550 nm assuming a CoSi2 stripe in p-type Si. End-fire coupled responsivities of about 0.1 A/W and minimum detectable powers of about −20 dBm are predicted at room temperature.
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Schottky Contact surface plasmon detector integrated with an asymmetric metal stripe waveguide
Applied Physics Letters, 2009Co-Authors: Ali Akbari, Pierre BeriniAbstract:A silicon-based Schottky Contact photodetector integrated into a finite width asymmetric metal stripe supporting short-range surface plasmon polaritons is presented. Input optical energy is coupled into a bound mode supported by the stripe, leading to total absorption of in-coupled energy. The absorbed energy excites carriers in the metal stripe, some of which cross the Schottky barrier (internal photoemission) leading to a photocurrent under reverse bias. Significant enhancement in the quantum efficiency is observed for a thin metal stripe due to multiple internal reflections of excited carriers. The device holds promise for short-reach high-speed optical interconnects and silicon-based photonic circuitry.
Nosang V Myung - One of the best experts on this subject based on the ideXlab platform.
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palladium single walled carbon nanotube back to back Schottky Contact based hydrogen sensors and their sensing mechanism
ACS Applied Materials & Interfaces, 2014Co-Authors: Miluo Zhang, Lauren L Brooks, Nicha Chartuprayoon, Wayne Bosze, Yongho Choa, Nosang V MyungAbstract:A Schottky Contact-based hydrogen (H2) gas sensor operable at room temperature was constructed by assembling single-walled carbon nanotubes (SWNTs) on a Si/SiO2 substrate bridged by Pd microelectrodes in a chemiresistive/chemical field effect transistor (chemFET) configuration. The Schottky barrier (SB) is formed by exposing the Pd–SWNT interfacial Contacts to H2 gas, the analyte it was designed to detect. Because a Schottky barrier height (SBH) acts as an exponential bottleneck to current flow, the electrical response of the sensor can be particularly sensitive to small changes in SBH, yielding an enhanced response to H2 gas. The sensing mechanism was analyzed by I–V and FET properties before and during H2 exposure. I–Vsd characteristics clearly displayed an equivalent back-to-back Schottky diode configuration and demonstrated the formation of a SB during H2 exposure. The I–Vg characteristics revealed a decrease in the carrier mobility without a change in carrier concentration; thus, it corroborates that...
Zhaojun Lin - One of the best experts on this subject based on the ideXlab platform.
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The influence of Schottky Contact metals on the strain of AlGaN barrier layers
Journal of Applied Physics, 2008Co-Authors: Zhaojun Lin, Jianzhi Zhao, Timothy D. Corrigan, Zhen Wang, Zhidong You, Zhanguo WangAbstract:Ir and Ni Schottky Contacts on strained Al0.25Ga0.75N/GaN heterostructures, and the Ni Schottky Contact with different areas on strained Al0.3Ga0.7N/GaN heterostructures have been prepared. Using the measured capacitance-voltage curves and the current-voltage curves obtained from the prepared Schottky Contacts, the polarization charge densities of the AlGaN barrier layer for the Schottky Contacts were analyzed and calculated by self-consistently solving Schrodinger's and Poisson's equations. It is found that the polarization charge density of the AlGaN barrier layer for the Ir Schottky Contact on strained Al0.25Ga0.75N/GaN heterostructures is different from that of the Ni Schottky Contact, and the polarization charge densities of the AlGaN barrier layer for Ni Schottky Contacts with different areas on strained Al0.3Ga0.7N/GaN heterostructures are different corresponding to different Ni Schottky Contact areas. As a result, the conclusion can be made that Schottky Contact metals on strained AlGaN/GaN heterostructures have an influence on the strain of the AlGaN barrier layer. (C) 2008 American Institute of Physics.
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influence of ni Schottky Contact area on two dimensional electron gas sheet carrier concentration of strained algan gan heterostructures
Journal of Applied Physics, 2006Co-Authors: Zhaojun LinAbstract:The influence of Ni Schottky Contact area on two-dimensional electron-gas (2DEG) sheet carrier concentration of strained AlGaN∕GaN heterostructures has been investigated by depositing different areas of Ni Schottky Contact on the structure. With the measured capacitance-voltage (C-V) curves, the 2DEG sheet carrier concentrations with different Ni Schottky Contact areas were calculated. It is shown that with the increased area of Ni Schottky Contact on strained AlGaN∕GaN heterostructures, the 2DEG sheet carrier concentration is decreased, and when the area of Ni Schottky Contact is increased to some extent, the decreased 2DEG sheet carrier concentration tends to be constant. A hypothetic model of the interaction among the electrons of Ni Schottky metal, the surface donor states of AlGaN barrier layer, and 2DEG electrons in strained AlGaN∕GaN heterostructures is proposed to explain the above results. The current-voltage (I-V) characteristics for the different areas of Ni Schottky Contact confirm the results...
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Influence of Ni Schottky Contact area on two-dimensional electron-gas sheet carrier concentration of strained AlGaN/GaN heterostructures
Journal of Applied Physics, 2006Co-Authors: Zhaojun LinAbstract:The influence of Ni Schottky Contact area on two-dimensional electron-gas (2DEG) sheet carrier concentration of strained AlGaN∕GaN heterostructures has been investigated by depositing different areas of Ni Schottky Contact on the structure. With the measured capacitance-voltage (C-V) curves, the 2DEG sheet carrier concentrations with different Ni Schottky Contact areas were calculated. It is shown that with the increased area of Ni Schottky Contact on strained AlGaN∕GaN heterostructures, the 2DEG sheet carrier concentration is decreased, and when the area of Ni Schottky Contact is increased to some extent, the decreased 2DEG sheet carrier concentration tends to be constant. A hypothetic model of the interaction among the electrons of Ni Schottky metal, the surface donor states of AlGaN barrier layer, and 2DEG electrons in strained AlGaN∕GaN heterostructures is proposed to explain the above results. The current-voltage (I-V) characteristics for the different areas of Ni Schottky Contact confirm the results...
