Low Junction Capacitance Research Articles

Junction temperature prediction method of GaN HEMT power devices based on accurate on-voltage testing

Compared with Si devices, GaN HEMT has lower on-resistance, lower junction capacitance, higher switching frequency, higher switching speed and higher junction temperature capability. It is widely used in automotive, aerospace and other fields. Severe environments may cause the junction temperature of GaN-HEMT to be too high, and excessive temperature is the main reason for power device failure. In order to ensure stable operation of GaN devices under harsh conditions, it is important to extract junction temperature information of semiconductor devices simply and effectively. However, most of the existing junction temperature prediction methods are not applicable to GaN HEMT devices due to its high switching speed and high requirement of prediction accuracy. Thus, we proposed a new method based on an accurate on-voltage clamp circuit to predict the junction temperature of GaN HEMT devices. The interrelation between the on-resistance and the junction temperature is analyzed, and the temperature coefficient is calibrated to obtain the corresponding relationship between the characterization quantity and the junction temperature. The on-resistance testing circuit suitable for GaN device is given and analyzed in detail. Finally, the conduction resistance testing circuit is used to predict the junction temperature of GaN devices, achieving extremely high accuracy. Experiments have verified under 100 ℃, the predicted junction temperature and the actual junction temperature have achieved more than 90% coincidence.

Ultrafast self-powered visible blind UV photodetectors based on MgZnO vertical Schottky junction in crossbar geometry

In order to achieve ultrafast response in MgZnO based self-powered Schottky type photodetectors, it is crucial to decrease both the junction capacitance and carrier transit time. To meet these criteria, Au/MgZnO/ITO Schottky junction photodetectors have been realised in crossbar pattern, wherein the thickness of the MgZnO thin film deposited on patterned ITO-glass substrate is ∼ 200 nm and the cross-sectional area of the devices is 0.032 mm2. The semi-transparent 10 nm Au electrode on top of the MgZnO film serves as the Schottky electrode through which light enters the devices. The vertical geometry of the crossbar pattern and the associated small device cross-section results in a low junction capacitance of the devices of ∼ 27 pF at zero bias, which in turn produces very fast visible blind self-powered ultraviolet (UV) photoresponse with both the rise and fall times of ∼ 1.5 μs, that is hitherto unreported for MgZnO based Schottky junction photodetectors. The devices also demonstrate a peak responsivity of ∼ 49 mA/W at ∼ 280 nm with a cut-off wavelength of 336 nm. These Au/MgZnO/ITO Schottky photodetectors in crossbar pattern, with optimized device area, could be useful in applications requiring fast response, such as UV communication and UV imaging.

Area and Bandwidth Enhancement of an n+/p-Well Dot Avalanche Photodiode in 0.35 μm CMOS Technology.

This paper presents a CMOS-integrated dot avalanche photodiode (dot-APD) that features a small central n+/p-well hemispherical cathode/p-well structure circularly surrounded by an anode ring. The dot-APD enables wide hemispherical depletion, charge collection from a large volume, and a small multiplication region. These features result in a large light-sensitive area, high responsivity and bandwidth, and exceptionally low junction capacitance. The active area can be further expanded using a multi-dot structure, which is an array of several cathode/p-well dots with a shared anode. Experimental results show that a 5 × 5 multi-dot APD with an active area of 70 μm × 70 μm achieves a bandwidth of 1.8 GHz, a responsivity of 9.7 A/W, and a capacitance of 27 fF. The structure of the multi-dot APD allows for the design of APDs in various sizes that offer high bandwidth and responsivity as an optical detector for various applications while still maintaining a small capacitance.

High-Power Microwave Limiters Using Recess-Free AlGaN/GaN Schottky Barrier Diodes

In this letter, a thin-barrier AlGaN/GaN Schottky barrier diode (SBD) is proposed and implemented in a three-stage high-power RF limiter module. Benefited from the thin-barrier epitaxy, a recess-free process in the Schottky region is allowed to avoid the plasma damage, resulting in low ON-resistance of 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> and high withstand voltage characteristics. In addition, the proposed SBDs have achieved a low junction capacitance of 0.35 pF at 0 V bias and a turn-on voltage of 0.5 V. With the optimized SBD and well-designed matching circuits, the limiter has reached a high power capacity of over 10 W in continuous wave (CW), 20 W in pulse mode, and a fast recovery time of 30 ns at a frequency of 3.5 GHz, exhibiting better characteristics than traditional limiters. Both simulation and measured results agree with each other. It indicates that the AlGaN/GaN-based SBD is promising for high-power and high-frequency limiters.

Design of film supported single mesa Schottky diodes for above 1THz application with submicron T-junction

A high-performance terahertz Schottky barrier diode (SBD) with a film-supported single mesa structure featuring a low structural parasitic with extremely low dielectric loss is reported in this brief. The fabricated substrate-free SBD is supported with a 2–3 µm polymer film using a low parasitic coupling capacitor of about 0.12 fF. It significantly reduces the electromagnetic coupling effect between the anode and cathode pads by 90% compared with the traditional structure of the same size. To reduce the Schottky junction capacitance at the anode, a submicron T-junction process is used with a low junction capacitance of 0.15 fF. The cutoff frequency calculated by the total capacitance of the diode is up to 4 THz. The substrate-free terahertz monolithic integration circuit based on this film-supported single mesa SBD has better performance in reducing the circuit dielectric loss, exhibiting a remarkable potential for high-frequency applications.

Rapid and up-scalable manufacturing of gigahertz nanogap diodes

The massive deployment of fifth generation and internet of things technologies requires precise and high-throughput fabrication techniques for the mass production of radio frequency electronics. We use printable indium-gallium-zinc-oxide semiconductor in spontaneously formed self-aligned <10 nm nanogaps and flash-lamp annealing to demonstrate rapid manufacturing of nanogap Schottky diodes over arbitrary size substrates operating in 5 G frequencies. These diodes combine low junction capacitance with low turn-on voltage while exhibiting cut-off frequencies (intrinsic) of >100 GHz. Rectifier circuits constructed with these co-planar diodes can operate at ~47 GHz (extrinsic), making them the fastest large-area electronic devices demonstrated to date.

Novel RF energy harvesting using Rectenna

In this paper an experimental RF energy harvester using rectifying antenna (rectenna) to harvest ambient energy from cellular device operating at 900 MHz GSM band is proposed. The circuit is a combination of antenna and rectifying circuit using Schottky barrier diode for microwave (RF) to DC conversion. The performance results of the rectenna shows radiation efficiency of around 58.81%, gain of 3.9 dB and directivity of 5.972 dBi. The proposed rectenna design can prove to be a low cost device for wireless power transmission and RF energy harvesting. The prototype is fabricated with simulated and measured results in good agreement, having a return loss of 21 dB at frequency of around 885 MHz. The overall efficiency is enhanced by using ISS351-TB-E Schottky diode which is categorized by a low junction capacitance and a low threshold voltage to achieve higher conversion efficiency.

Nonlinearity and parameterization of Schottky diodes-based battery-free harmonic transponder for millimeter-wave 5G applications

Deployment of 5G network infrastructure is a timely opportunity for millimeter-sized battery-free sensors. However, millimeter-wave (mmW) devices often suffer from high conversion loss and path loss that are heavily limiting their communication/detection distance, especially for the case of harmonic transponders based on Schottky diodes. A deep and comprehensive parametric understanding of the second-harmonic generation mechanism of Schottky diodes in the mmW 5G bands can help us to identify suitable diodes or guide diode fabrication to reduce transponder conversion loss. This work reveals that both diode nonlinear junction resistance and capacitance contribute to the second-harmonic generation across the mid-band (sub-7 GHz) and high-band (mmW) 5G frequency bands. However, the nonlinear junction capacitance dominates the second-harmonic generation in the mmW bands. Without Joule heating during the conversion process, the capacitive nonlinearity is more efficient than the resistive nonlinearity, which means that a Schottky diode with a lower junction capacitance will efficiently reduce its associated conversion loss. The VDI GaAs zero bias diode with a low zero bias nonlinear junction capacitance (19.19 fF) shows superior conversion loss performance, which indicates that it can be employed to enhance the detection distance of battery-free harmonic transponders in the mmW 5G bands.

Detection, Acquisition and Processing of Fluorescence from Cold Atoms in Cesium Fountain Primary Frequency Standard at NPL, India

In this paper, detailed geometry of the detection chamber, configuration of detection probe laser beams, data acquisition and processing techniques of the cold atoms in Cs atomic fountain primary standard at NPL, India has been discussed. The S/N ratio in the detected atom count was too low to make a valid estimate of signal. By implementing an efficient design of detection hardware (especially changing photodiode with lower junction capacitance) and software, the S/N ratio in NPLI-CsF1 has been improved significantly (~ 10 times). Details of the detection hardware and software used for better processing of the signal are given in this paper. This paper also depicts the precise computer control for data processing and the improvements in signal to noise ratio in the context of fountain operation.

Enhanced solar-cell efficiency via fabricated zinc sulfide nanocrystalline thin film-based Schottky diodes as a bypass: An experimental and theoretical investigations

This work represents experimental and theoretical investigations on the electrical characteristics of ZnS nanocrystalline thin films synthesized via sonicated (UCBD) and un-sonicated (CBD) chemical bath deposition technique and the fabrication of Schottky junction diodes, for potential solar cell incorporation and other opto-electronic applications. The sonication induced ZnS nanocrystalline thin films (SNP) at frequency 20 kHz–1 MHz and without sonication induced ZnS nanocrystalline thin films (NP) deposited on an indium tin oxide (ITO) substrate. A rapid thermally evaporated lightly doped Ag on SNP and NP-ZnS transparent thin films in the high range of vacuum (~10−6 Torr), has been achieved. The current density-voltage (J-V) and capacitance-voltage (C-V) measurements of fabricated Schottky diodes were carried out employing a potentiostat device. The enhanced performance of fabricated Schottky devices has been quantified by analyzing their J-V characteristics using established Landauer transport formalism. Ideal diode behavior has been confirmed by a low voltage drop of 0.35 V, and low junction capacitance ~3.21 nF across fabricated Schottky diodes. The maximum blockage of leakage current across fabricated Schottky diodes have been detected as compared to the available commercial diodes. The Landauer transport model found to be excellent fitting for understanding the electron transport mechanism for these fabricated diodes. The Fermi energy level pinned near effective gap center that shifts under the bias condition due to the metal induced gap states. The Schottky diodes as a bypass in solar cell panel demonstrates the significant enhancement in photo-response and efficiency of solar cell in the presence of sunlight.

Quad-Band Rectenna for RF Energy Harvesting System

The design of multiband microstrip rectenna for radio frequency energy harvesting applications is presented in this paper. The designed antenna has good performance in the GSM-900/1800, WiFi and WLAN bands. In addition, the rectifier circuit is designed at multi resonant frequencies to collect the largest amount of RF ambient power from different RF sources. The developed antenna is matched with the rectifier at four desired frequencies using several rectifier branches to collect the largest of RF power. The proposed rectenna is printed on FR4 substrate with modified ground plane to achieve suitable impedance bandwidth. The proposed antenna consists of elliptical radiating plane with stubs and stepped modified ground plane. The rectenna resonates at quad frequency bands at (GSM 900/1800, WiFi band and WLAN bands) with rectifier power conversion efficiency up to 56.4% at 0 dBm input power using the HSMS-2850 Schottky diode. The efficiency is more enhanced by using SMS-7630-061 Schottky diode which is characterized by a low junction capacitance and a low threshold voltage to achieve higher conversion efficiency up to 71.1% at the same 0 dBm input power for the same resonating frequency band.

A 5.8-GHz High-Power and High-Efficiency Rectifier Circuit With Lateral GaN Schottky Diode for Wireless Power Transfer

In this letter, we propose to implement a microwave lateral GaN Schottky barrier diode (SBD) in a designed 5.8-GHz rectifier circuit for future high-power and high-efficiency wireless power transfer. The low-pressure chemical vapor deposition SiN-passivated lateral GaN SBD demonstrates a low turn- on voltage of 0.38 V, a low on -resistance of 4.5 Ω, a low junction capacitance of 0.32 pF at 0-V bias, and a high breakdown voltage of 164 V, which are essentials for a high-efficiency and high-power rectifying application. By incorporating this lateral GaN SBD in a well-designed 5.8-GHz rectifier circuit, an unprecedented combination of high efficiency and high power is achieved simultaneously. The rectifier circuit demonstrates a high RF/dc conversion efficiency ( η RF/DC) of 71 ± 4.5% with an input power ( P in) of 2.5 W and η RF/DC = 50 ± 4.5% with P in = 6.4 W per single diode, showing the great promise of embracing lateral GaN SBD for future wireless high-power transfer application.

Design of high speed InGaAs/InP one-sided junction photodiodes with low junction capacitance

A high speed InGaAs/InP one-sided junction photodiode (OSJ-PD) with low junction capacitance is presented and investigated for the first time. Compared with the well known uni-traveling carrier photodiode (UTC-PD), the OSJ-PD has the advantages of simpler epitaxial layer structure and lower junction capacitance, while maintaining the characteristics of high speed and high output power. The OSJ-PD is studied by simulation. The performance characteristics of OSJ-PD including internal electric field distribution, energy band diagram, frequency response, photocurrent and junction capacitance, are carefully studied.

Design of modified InGaAs/InP one-sided junction photodiodes with improved response at high light intensity.

A modified InGaAs/InP one-sided junction photodiode (MOSJ-PD) is presented for the first time. The MOSJ-PD is proposed from the one-sided junction photodiode by inserting a cliff layer into the absorption layer. Compared to the modified uni-traveling carrier photodiode, the MOSJ-PD has the advantages of simpler epitaxial layer structure and lower junction capacitance. In the MOSJ-PD, the space charge effect at high light intensity can be suppressed. Thus, both 3-dB bandwidth and output current can be improved simultaneously. The performance characteristics of the MOSJ-PD, including energy band diagram, internal electric field, frequency response, photocurrent, and responsivity, are carefully studied.

A monolithically integrated butt-coupled 3D bulk CMOS Si photodetector array with a fiber couplers platform on a single-chip

A linear array of 55 butt-coupled three-dimensional (3D) photodetectors based on a silicon (Si) substrate is presented with a monolithically integrated tapered U-grooves platform for embedding strands of a fiber bundle into a Si chip. This structure enables a direct coupling of the fiber strands with a diameter of Ø30μm to the vertical photoactive areas of a Si detector array one by one. A vertically 3D large photoactive area ∼30μm×40μm+2(30μm×10μm) is formed separated from the n-i-p structure on the top side to achieve a high performance butt-coupled photodetector. The prototype is fabricated by employing 3D CMOS and MEMS technology on a p-type Si wafer. The implementation of 30μm-deep double-trench isolation with the formation of a shallow n+-p junction and SiO2-liner over the trench sidewalls as well as SU-8 filling of the trenches realizes a high efficiency detector isolation and a low dark current of 1.14nA at 2V reverse bias. The maximum photoresponsivities under illumination with 470nm, 525nm, and 631nm LEDs light are observed under the lowest incident light power. A low junction capacitance of ∼30+/−3fF at 2.4V reverse bias is measured at a frequency of 1MHz. Therefore, this approach brings outstanding features for non-telecom and high efficiency remote optical fiber sensor applications at the wavelengths of 470nm, 525nm, and 631nm in high electromagnetic field environments.

A new family of field-stable and highly sensitive SQUID current sensors based on sub-micrometer cross-type Josephson junctions

We report on the development of a new family of superconducting quantum interference device (SQUID) current sensors based on sub-micron cross-type Josephson tunnel junctions. Their low total junction capacitance permits high usable voltage swings of more than 100 μV and exceptional low noise of the SQUIDs at 4.2 K. Integrated rf-filters as well as high tolerable background fields during cool-down of up to 9.6 mT enable their highly reliable and easy use. With input coil inductances ranging from 10 nH to 2.8 μH and current sensitivities and coupled energy resolution down to 65 fA Hz–1/2 and below 10 h, respectively, they are a versatile tool for numerous applications.

Large-area silicon nanowire Schottky junction photodetector with tunable absorption and low junction capacitance

Silicon photodetectors for operation in the near-infrared with a sufficient responsivity and high-speed operation are currently needed as scalable, CMOS compatible components for photonic and communication applications. Photodetectors based on semiconductor nanowire structures with dielectric planarization enable larger active optical areas and higher operating speeds than planar devices due to reduced junction capacitance and enhanced absorption. Here, we report on the fabrication and characterization of a silicon nanowire photodetector with dielectric infilling and a transparent indium tin oxide (ITO) Schottky contact. Optical simulations show that the absorbed power can be confined at the top of the nanowire array, enabling efficient operation in the near-infrared. This is despite the relatively low absorption coefficient for silicon in this wavelength range in addition to the design of the nanowire array to have a low fill factor compared to the bulk material in order to minimize the junction capacitance. The responsivity of this device is >0.3 A W−1 at a reverse bias of 2 V and the junction capacitance is 8 ± 2 nF cm−2, which are respectively comparable and lower than the values expected for a planar silicon Schottky junction photodetector with a similar active area.

56 Gb/s Germanium Waveguide Electro-Absorption Modulator

We report a Germanium waveguide electro-absorption modulator with electro-optic bandwidth substantially beyond 50 GHz. The device is implemented in a fully integrated Si photonics platform on 200 mm silicon-on-insulator wafers with 220 nm top Si thickness. Wide open eye diagrams are demonstrated at 1610 nm operation wavelength for nonreturn-to-zero on-off keying (NRZ-OOK) modulation at data rates as high as 56 Gb/s. Dynamic extinction ratios up to 3.3 dB are obtained by applying drive voltages of 2 V peak-to-peak, along with an optical insertion loss below 5.5 dB. The device has a low junction capacitance of just 12.8 fF, resulting in 12.8 fJ/bit of dynamic and ∼1.2 mW of static power consumption in typical operating conditions. Wafer-scale performance data are presented and confirm the manufacturability of the device. The demonstrated modulator shows great potential for realizing high-density and low-power silicon photonic transceivers targeting short-reach optical interconnects at serial data rates of 56 Gb/s and beyond.

1200 V SiC Schottky Rectifiers optimized for ≥ 250 °C operation with low junction capacitance

Electrical Characteristics of Industry's first commercially available 1200 V rated SiC Schottky rectifiers, specially designed for operation at ≥ 250 °C are presented. These high-temperature SiC rectifiers fabricated in 1, 5, and 20 A current ratings feature reverse leakage currents of &amp;lt; 3 mA/cm2 at 1200 V up to temperatures as high as 300 °C. GeneSiC's 1200 V/20A High Temperature Schottky (designated SHT) rectifier offers a 10x reduction in leakage current and a 23% reduction in junction capacitance when compared to its nearest SiC Schottky rectifier competitor. In addition, these SHT rectifiers demonstrate superior surge-current ratings, and temperature-independent switching capability up to their rated junction temperatures.

Fabrication of Schottky diodes for terahertz imaging

In this paper we present design, fabrication and characterization of Schottky terahertz diodes. The diode is based on a Ti/n-GaAs junction with very low junction capacitance. T-gate technology, based on trilayer of electronic resists and electron-beam lithography, and air-bridge technique have been used to obtain Schottky diodes with cutoff frequency in the THz range. The device fabrication process is fully planar and suitable for integration in monolithic arrays for active spectroscopic imaging.