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Oxidized Metal Schottky Contacts on (010) β-Ga2 O 3
摘要： Oxidized Ir, Pd, Pt, Ag, and Au Schottky contacts (SCs) were fabricated on (010) β-Ga2O3 single crystal substrates via reactive rf sputtering using an O2:Ar plasma. The use of in-situ oxidizing conditions resulted in SCs with very high rectifying barriers in excess of 2.0 eV for all the metals investigated, representing an increase of 0.4 to 0.9 eV compared to the corresponding plain metal versions. Both the plain and oxidized metal SCs showed evidence of Fermi Level pinning with their laterally homogeneous barrier heights lying in narrow ranges of ~1.3 to 1.5 eV and ~2.2 to 2.4 eV, respectively, with little correlation with metal work function. This was attributed to the influence of metal-induced oxygen vacancies and gap states at the SC interface, respectively. The very high barriers of the oxidized SCs resulted in excellent high temperature performance with ~10 orders of magnitude of rectification at 180 oC, indicating the potential of this technique for the fabrication of high temperature unipolar devices.
关键词： Metal Induced Gap States,Fermi Level Pinning,Oxygen Vacancies,Semiconductor Interfaces,Schottky Diodes
更新于2025-09-23 15:22:29
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Electrical characterization of HVPE GaN containing different concentrations of carbon dopants
摘要： A comprehensive study of the electrical characteristics in Schottky diodes made of GaN:C grown by HVPE technology has been reported. The Schottky junctions were made of Ni/Au (25/200 nm) metal stack and ohmic contacts were fabricated by the Ti/Al/Ni/Au (30/90/20/100 nm) e-beam deposition of the metal thin-films followed by the rapid thermal annealing. A good quality of the fabricated Schottky diodes has been proved by considering the transient shape using a pulsed technique of the barrier evaluation under linearly increasing voltage (BELIV). The concentrations of equilibrium carriers of 1×1011 cm-3 and of 2×1010 cm-3 have been evaluated for relatively low and high carbon density doped samples, respectively, using photo-capacitance characteristics dependent on excitation intensity. The effective mobility of carriers of μeff=610 cm2/Vs has been estimated by considering the serial resistance variations dependent on excitation density, through analysis of delay times appeared in formation of peaks within BELIV transients. The optical deep level transient spectroscopy has shown that thermal emission from the rather shallow centres prevails. The centres, ascribed to vacancies as well as to carbon on Ga site, have been identified. It has been demonstrated that Schottky junctions made of heavy carbon doped (NC≥1018 cm-3) HVPE GaN material are capable to withstand voltages of ≥300 V.
关键词： barrier evaluation by linearly increasing voltage pulsed technique,transient current technique,Schottky diodes,carbon doped HVPE GaN grown on Ammono substrates,deep level transient spectroscopy
更新于2025-09-23 15:21:21
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Absence of Evidence for Fixed Charge in Metal-Aluminum Oxide-Silicon Tunnel Diodes
摘要： Here, a controlled variation in the fixed charge density (NF) and thickness of aluminum oxide tunnel insulators is reported, and the impact on Schottky barrier height ΦB in metal–insulator–semiconductor (MIS) diodes is studied. Analysis of metal–aluminum oxide–silicon capacitor structures indicates a change in NF from t1 × 1012 cm?2 in as-deposited films to ?1 × 1012 cm?2 in annealed films. An analytical model and numerical device physics simulations are used to predict changes in ΦB based on these changes in NF and alumina thickness. Surprisingly, Mott–Schottky derived ΦB values did not follow the trends predicted by these electrostatic models. In fact, there seems to be no discernable effect of NF in diodes with alumina thicknesses below 2 nm, contrary to contactless measurements of the fixed charge of films of similar thickness. The ΦB trends are better explained by a dipole model. It is further shown that in as-deposited MIS diodes, the dipole is a function of alumina layer thickness, whereas in annealed MIS diodes, the dipole and ΦB were roughly constant independent of alumina thickness. These data suggest a strategy by which the ΦB of MIS tunnel contacts can be controlled and which has implication for the design of electrical contacts.
关键词： atomic layer deposition,fixed charges,silicon,barrier height,Schottky diodes
更新于2025-09-23 15:21:01
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[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Impact of post deposition annealing of ZrO <sub/>2</sub> insulating layer on the performance of GaN metal-semiconductor-metal ultraviolet photodetectors
摘要： GaN metal–semiconductor–metal (MSM) ultraviolet photodetectors without and with annealed ZrO2 insulating layers are successfully fabricated. It is found that the dark current is reduced by 3 times post annealing of the oxide layer. GaN MSM photodetectors exhibit large internal gain which can be explained by considering the presence of hole traps in oxide layer. Further, reduction in gain and increase in transient response time of photodetectors post annealing of ZrO2 layer reveal that the density of shallow trap states is considerably reduced by the annealing step. It is noticed that though the response of all the states is affected by the annealing but the fast component of photoresponse is rather severely hampered. The present investigations clearly demonstrate that reduction of dark current is not the sole criteria for improving the performance of a photodetector. Rather, transient response of the device and hence the band width of the device along with the leakage current and gain should be taken into the consideration for qualifying the overall performance of the photodetectors.
关键词： Photoresponse,GaN,Schottky diodes,Responsivity,I-V
更新于2025-09-16 10:30:52
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A 135-150-GHz Frequency Tripler Using SU-8 Micromachined WR-5 Waveguides
摘要： This article presents a 135–150-GHz Schottky diode-based bias-less frequency tripler based on SU-8 micromachined WR-5 waveguides. The waveguides consist of five 432-μm-thick silver-plated SU-8 layers, which house the diode chip and form the output matching network. The input matching circuit is realized in a computer numerical control (CNC) milled waveguide filter, which also provides support and thermal sink to the SU-8 waveguides. Considering the low thermal conductivity of the SU-8 material, auxiliary metallic thermal paths are designed, and the impact of these is discussed through thermal modeling. The thermal simulations show that under 50-mW power dissipation in the diode anodes, the maximum temperature of the SU-8 tripler is predicted to be 346 K at the diode junction, only 7 K higher than in an entirely metal equivalent. The tripler was measured to have a conversion loss of 16–18 dB and the input return loss is better than 18 dB. This work demonstrates that SU-8 micromachined waveguides can be used to package high-frequency semiconductor components, which, like other photolithography-based processes such as silicon deep reactive ion etching (Si-DRIE), has the potential for submicrometer feature resolution.
关键词： multiplier,SU-8 waveguide,planar Schottky diodes,Filter matching
更新于2025-09-16 10:30:52
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Topological and electrical properties of capped and annealed (0001) hydride vapor phase epitaxy GaN films on sapphire
摘要： In light of the necessity to anneal GaN to activate implanted dopants, the effects of the annealing temperature and time, the quality of the hydride vapor phase epitaxy grown GaN film, the quality of the annealing cap, and the effects of the stresses generated by the difference in the coefficients of thermal expansion of the film and the substrate are examined topographically using atomic force microscopy, and electrical measurements are made on Schottky diodes fabricated on the annealed samples. The results show that thermal decomposition begins at threading edge dislocations that form polygonized small angle grain boundaries during the annealing process; donor defects, probably nitrogen vacancies, are formed near the surface; and the donors are created more quickly when the annealing temperature is higher, the annealing time is longer, and the thermal stresses on the annealing cap are greater. The results suggest that the maximum annealing temperature is ～1300 °C, and at that annealing temperature, the annealing time should not exceed 4 min.
关键词： thermal decomposition,nitrogen vacancies,Schottky diodes,atomic force microscopy,GaN,annealing
更新于2025-09-11 14:15:04
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A High Linearity, 8-<i>GSa</i>/<i>s</i> Track-and-Hold Amplifier in GaAs HBT Technology
摘要： A high linearity full differential 8 GSa/s track-and-hold amplifier (THA) is presented in this paper. The proposed THA is designed and implemented using 2-μm GaAs HBT technology to be targeted for faster operation in sampling systems at a clock frequency of GHz. In this THA, an alternative switch emitter follower (SEF) is used as a switching stage with a Schottky diode for hold-mode isolation enhancement and high–speed operation. In conjunction with well-designed input buffer allows us to achieve high linearity and comparable dynamic performance. Measured small signal -3 dB bandwidth, and hold-mode isolation are better than 3.6 GHz and 40 dB, respectively. The prototype achieves a spurious-free dynamic range (SFDR) of 43.9 dB at 0.5 GHz and an average total harmonic distortion (THD) below -40 dBc up to a first Nyquist frequency of 4 GHz. This work has the potential for wideband, high speed and low distortion analog to digital converter (ADC) used in the future direct sampling systems.
关键词： nonlinear distortion,track-and-hold,high-speed sampling,Schottky diodes,gallium arsenide,MMICs
更新于2025-09-09 09:28:46
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190 GHz high power input frequency doubler based on Schottky diodes and AlN substrate
摘要： This paper presents the design and development of a 190 GHz Schottky-diode frequency doubler (×2 multiplier) which can handle up to 260 mW input power. In order to increase the power handling capability, a modeling approach incorporating computer-aided design (CAD) load-pull techniques to characterize the diode performance is proposed. By the use of this approach, e?ects of several critical diode parameters on the power handling issue are quantitatively investigated and based on the analysis, a discrete diode chip is designed for the doubler. To ensure rapid heat sink in the doubler circuitry, low cost aluminum nitride ceramic (AlN) is selected as the dielectric material of the circuit substrate, which has signi?cantly better thermal conductivity compared with currently widely-used fused quartz. The doubler circuitry is based on a balanced con?guration, which brings a merit of avoiding the use of a ?lter for the input and output signal isolation. The doubler circuit is optimized by co-simulation using ANSYS’s HFSS and Keysight’s ADS. The measurements show that the doubler can handle up to 260 mW input power with a power conversion e?ciency of nearly 8%, resulting in 20 mW output power at 193 GHz.
关键词： high power,AlN substrate,Schottky diodes,CAD load-pull,terahertz multiplier
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - A Compact Room-Temperature 510-560 GHz Frequency Tripler with 30-mW Output Power
摘要： We report on a compact high-power 510-560 GHz GaAs Schottky diode based frequency tripler with enhanced power handling capabilities, showing a world-record measured peak power of 30 mW, at room-temperature, when pumped with 350-400 mW. This corresponds to a ten times better performance than previously reported sources in this frequency range. The increase in power handling capabilities is achieved by using an improved epitaxial structure together with an on-chip power combined topology that allows to combine several multiplying structures onto a single chip. The chip also exhibits a state-of-the- art conversion efficiency of 8-9% without any correction for the losses in fixtures/transitions used for the tests.
关键词： Schottky diodes,frequency multipliers,submillimeter-wave technology,terahertz technology.,Submillimeter-wave sources
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - High Power High Efficiency 270-320 GHz Source Based on Discrete Schottky Diodes
摘要： A 300 GHz source based on discrete Schottky diodes technology is reported in this work. The high frequency part developed by ACST consists of two high power and high efficiency doublers, one at 135-160 GHz and a second one at 270-320 GHz. Both doublers feature a single chip per module and do not use any power combining techniques. The 150 GHz and 300 GHz doublers are able to handle more than 400 mW and 100 mW input power and provide more than 140 mW and 30 mW output power, respectively. This is the most powerful 300 GHz source reported based on discrete Schottky diodes at this frequency range without using power combining.
关键词： Schottky diodes,high efficiency,high power,frequency multipliers
更新于2025-09-04 15:30:14