Showing papers on "Schottky diode published in 2001"

Gain mechanism in GaN Schottky ultraviolet detectors

Abstract: Schottky barrier GaN ultraviolet detectors, both in vertical and in lateral configuration, as well as in a metal–semiconductor–metal geometry were implemented. All devices exhibit a high gain at both reverse and forward bias. The photoresponse in the forward bias is in the positive current direction. We attribute the gain to trapping of minority carriers at the semiconductor–metal interface. The excellent agreement between the calculated responsivity and the experiment indicates that the model is valid for all device structures under study, and represents a unified description of gain mechanism in GaN Schottky detectors.

Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottky diodes

Abstract: The reverse bias leakage current in macroscopic GaN Schottky diodes is found to be insensitive to barrier height. Using a scanning current–voltage microscope, we show that the reverse bias current occurs at small isolated regions, while most of the sample is insulating. By comparing the current maps to topographic images and transmission electron microscopy results, we conclude that reverse bias leakage occurs primarily at dislocations with a screw component. Furthermore, for a fixed dislocation density, the V/III ratio during the molecular beam epitaxial growth strongly affects reverse leakage, indicating complex dislocation electrical behavior that is sensitive to the local structural and/or chemical changes.

Commonly housed diverse semiconductor die

Abstract: A MOSFET die and a Schottky diode die are mounted on a common lead frame pad and their drain and cathode, respectively, are connected together at the pad. The pad has a plurality of pins extending from one side thereof. The lead frame has insulated pins on its opposite side which are connected to the FET source, the FET gate and the Schottky diode anode respectively by wire bonds. The lead frame and die are molded in an insulated housing and the lead frame pins are bent downwardly to define a surface-mount package.

SiC power diodes provide breakthrough performance for a wide range of applications

Abstract: The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions.

Electrical transport characteristics of Au/n-GaAs Schottky diodes on n-Ge at low temperatures

Abstract: The currenti?½voltage characteristics of Au/n-GaAs Schottky diodes grown by metal-organic vapor-phase epitaxy on Ge substrates were determined in the temperature range 80i?½300 K. The zero-bias barrier height for current transport decreases and the ideality factor increases at low temperatures. The ideality factor was found to show the T0 effect and a higher characteristic energy. The excellent matching between the homogeneous barrier height and the effective barrier height was observed and infer good quality of the GaAs film. No generationi?½recombination current due to deep levels arising during the GaAs/Ge heteroepitaxy was observed in this study. The value of the Richardson constant was found to be 7.04 A K?2 cm?2, which is close to the value used for the determination of the zero-bias barrier height.

GaN metal-semiconductor-metal ultraviolet photodetectors with transparent indium-tin-oxide Schottky contacts

Abstract: Indium-tin-oxide (ITO) layers were deposited onto n-GaN films and/or glass substrates by electron-beam evaporation. With proper annealing, we found that we could improve the optical properties of the ITO layers and achieve a maximum transmittance of 98% at 360 nm. GaN-based metal-semiconductor-metal (MSM) photodetectors with ITO transparent contacts were also fabricated. A maximum 0.12-A photocurrent with a photocurrent to dark current contrast higher than five orders of magnitude during ultraviolet irradiation were obtained for a photodetector annealed at 600/spl deg/C. We also found that the maximum photo responsivity at 345 nm is 7.2 and 0.9 A/W when the detector is biased at 5 and 0.5 V, respectively.

The future of power semiconductor device technology

Abstract: Power electronic systems have benefited greatly during the past ten years from the revolutionary advances that have occurred in power discrete devices. The introduction of power metal-oxide-semiconductor field-effect transistors (MOSFETs) in the 1970s and the insulated gate bipolar transistors (IGBTs) in the 1980s enabled design of very compact high-efficiency systems due to the greatly enhanced power gain resulting from the high input impedance of these structures. Recently, significant improvements in the performance of silicon-power MOSFETs has been achieved by using innovative vertical structures with charge coupled regions. Meanwhile, silicon IGBTs continue to dominate the medium- and high-voltage application space sue to scaling of their voltage ratings and refinements to their gate structure achieved by using very large scale integration (VLSI) technology and trench gate regions. Research on a variety of MOS-gated thyristors has also been conducted, resulting in some promising improvements in the tradeoff between on-state power loss, switching power loss, and the safe-operating-area. Concurrent improvements in power rectifiers have been achieved at low-voltage ratings using Schottky rectifier structures containing trenches and at high-voltage ratings using structures that combine junction and Schottky barrier contacts. On the longer term, silicon carbide Schottky rectifiers and power MOSFETs offer at least another tenfold improvement in performance. Although the projected performance enhancements have been experimentally demonstrated, the defect density and cost of the starting material are determining the pace of commercialization of this technology at present.

Controlled creation of a carbon nanotube diode by a scanned gate

Abstract: We use scanning gate microscopy to precisely locate the gating response in field-effect transistors (FETs) made from semiconducting single-wall carbon nanotubes. A dramatic increase in transport current occurs when the device is electrostatically doped with holes near the positively biased electrode. We ascribe this behavior to the turn-on of a reverse biased Schottky barrier at the interface between the p-doped nanotube and the electrode. By positioning the gate near one of the contacts, we convert the nanotube FET into a rectifying nanotube diode. These experiments both clarify a longstanding debate over the gating mechanism for nanotube FETs and indicate a strategy for diode fabrication based on controlled placement of acceptor impurities near a contact.

Nanometer-scale test of the Tung model of Schottky-barrier height inhomogeneity

Abstract: Tung has shown [Phys. Rev. B 45, 13 509 (1992)] that a range of ``nonideal'' behaviors observed in metal/semiconductor (MS) Schottky diodes could be quantitatively explained by assuming that specific microscopic distributions of nanometer-sized ``patches'' of reduced barrier height exist at the MS interface. Here we report a simultaneous microscopic and macroscopic test of this model as applied to $\mathrm{metal}/6H\ensuremath{-}\mathrm{SiC}$ Schottky diodes, by (1) measuring the nm-scale barrier-height distribution (BHD) of particular Schottky diodes using ultrahigh vacuum (UHV) ballistic electron emission microscopy (BEEM), (2) extending the Tung model to calculate the expected nm-scale BHD for particular parameter values, and (3) quantitatively relating the measured nm-scale BHD of a particular Schottky diode to its macroscopic $I\ensuremath{-}V$ characteristic. Our studies indicate that (1) for relatively ideal diodes, both the microscopic and macroscopic behaviors are explained well by the Tung model with a large coverage (g5%) of shallow patches, (2) the measured BHDs are nearly identical for relatively ideal and highly nonideal diodes, and (3) a simple Tung model can account for highly nonideal behavior only by assuming an unphysical patch distribution in which the excess current is dominated by a few patches in the extreme tail of the patch distribution. Our measurements instead suggest that all the diodes contain a broad ``intrinsic'' distribution of shallow patches, while the large excess current in highly nonideal diodes is due to a few large defects of extrinsic origin. This last conclusion is consistent with a recent study by Skromme and co-workers [J. Electron. Mater. 29, 376 (2000)].

Freewheeling diode reverse-recovery failure modes in IGBT applications

Abstract: In this paper, reverse-recovery failure modes in modern fast power diodes are investigated. By the aid of semiconductor device simulation tools, a better view is obtained for the physical process, and operating conditions at which both diode snappy recovery and dynamic avalanching occur during the recovery period in modern high-frequency power electronic applications. The work presented here confirms that the reverse-recovery process can by expressed by means of diode capacitance effects which influence the reverse-recovery characteristics. The paper also shows that the control of the carrier gradient and the remaining stored charge in the drift region during the recovery phase influence both failure modes and determine if the diode exhibits soft, snappy, or dynamic avalanche recovery characteristics.

Doping dependence of the barrier height and ideality factor of Au/n-GaAs schottky diodes at low temperatures

Abstract: The barrier height and ideality factor of Au/n-GaAs Schottky diodes grown by metal-organic vapor-phase epitaxy (MOVPE) on undoped and Si-doped n-GaAs substrates were determined in the doping range of 2.5 � 10 15 – 1 � 10 18 cm � 3 at low temperatures. The thermionic-emission zero-bias barrier height for current transport decreases rapidly at concentrations greater than 1 � 10 18 cm � 3 . The ideality factor also increases very rapidly at higher concentration and at lower temperature. The results agree quite well with thermionic field emission (TFE) theory. The doping dependence of the barrier height and the ideality factor were obtained in the concentration range of 2.5 � 10 15 – 1.0 � 10 18 cm � 3 and the results are well described using TFE theory. An excellent match between the homogeneous barrier height and the effective barrier height was observed which supports the good quality of the GaAs film. The observed variation in the zero-bias barrier height and the ideality factor can also be explained in terms of barrier height inhomogeneities in the Schottky diode. r 2001 Elsevier Science B.V. All rights reserved.

Semiconductor device with schottky electrode having high schottky barrier

Abstract: A carrier travel layer is formed on the substrate of a semiconductor device with a buffer layer interposed, and a spacer layer and carrier supply layer are then formed on this carrier travel layer. On the carrier supply layer are provided a source electrode and a drain electrode, and a gate electrode is provided on an interposed Schottky layer. The carrier supply layer is composed of AlGaN and has tensile strain. The Schottky layer is composed of InGaN and has compressive strain. A negative piezoelectric charge is induced on the carrier supply layer side of the Schottky layer, and a positive piezoelectric charge is induced on the opposite side of the Schottky layer, whereby a sufficient Schottky barrier height is obtained and leakage current is suppressed.

Comparison of GaN p-i-n and Schottky rectifier performance

Abstract: The performance of GaN p-i-n and Schottky rectifiers fabricated on the same wafer was investigated as a function of device size and operating temperature. There was a significant difference in reverse breakdown voltage (490 V for p-i-n diodes; 347 V for the Schottky diodes) and forward turn-on voltage (/spl sim/5 V for the p-i-n diodes; /spl sim/3.5 V for the Schottky diodes). Both types of device showed a negative temperature coefficient for reverse breakdown, with value -0.34/spl plusmn/0.05 V/spl middot/K/sup -1/.

GaN and InGaN Metal-Semiconductor-Metal Photodetectors with Different Schottky Contact Metals

Abstract: The characterizations of n-type doped GaN, p-type doped GaN and n-type doped In0.2Ga0.8N Schottky metal-semiconductor-metal (MSM) photodetectors were reported. The epilayers were grown on sapphire by metalorganic chemical vapor deposition (MOVCD). Schottky contacts were fabricated using Au, Ti, Ni and Pt metals. The dark and illuminated current–voltage characteristics of GaN and InGaN MSM photodetectors with different Schottky metals were studied. The n-GaN MSM photodetectors with Au Schottky contacts showed better responsivity than those with other metals and they were also better than Au/p-GaN and Ti/n-In0.2Ga0.8N MSMs. The effects of the pitch width between the interdigitate fingers and the thickness of Schottky metals on the characteristics of photocurrents were also studied.

Interface states density distribution in Au/n-GaAs Schottky diodes on n-Ge and n-GaAs substrates

Abstract: The current–voltage (I–V) and capacitance–voltage (C –V) characteristics of Au/n-GaAs Schottky diodes on n-Ge substrates are investigated and compared with characteristics of diodes on GaAs substrates. The diodes show the non-ideal behavior of I– V characteristics with an ideality factor of 1.13 and barrier height of 0.735 eV. The forward bias saturation current was found to be large (3 ×10 −10 A vs. 4.32 ×10 − 12 A) in the GaAs/Ge Schottky diodes compared with the GaAs/GaAs diodes. The energy distribution of interface states was determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective barrier height, though it is small. The interface states density was found to be large in the Au/n-GaAs/n-Ge structure compared with the Au/n-GaAs/n + -GaAs structure. The possible explanation for the increase in the interface states density in the former structure was highlighted. © 2001 Published by Elsevier Science B.V.

High resolution Schottky CdTe diode detector

Abstract: We describe recent progress on the use of Schottky CdTe diode detectors for spectrometry. The low leakage current of the CdTe diode allows us to apply a much higher bias voltage than was possible with previous CdTe detectors. For a relatively thin detector of 0.5-1 mm thickness, the high bias voltage results in a high electric field in the device. Both the improved charge-collection efficiency and the low-leakage current lead to an energy resolution of better than 600 eV full-width at half-maximum at 60 keV for a 2/spl times/2 mm/sup 2/ device without any charge-loss correction electronics. Large-area detectors with dimensions of 21/spl times/21 mm/sup 2/ are now available with an energy resolution of /spl sim/2.8 keV. Long-term stability can be easily attained for relatively thin (<1 mm) detectors if they are cooled or operated under a high bias voltage.

Injection- and space charge limited-currents in doped conducting organic materials

Abstract: Most conducting organic materials have a background p-type doping varying in the range 1015–1017 cm−3. We report results of a theoretical and experimental study of carrier transport in p-doped organic Schottky diodes. The theory given in this article shows that in a doped organic material with ohmic contacts the current is ohmic at low voltages. If the ohmic contact at the cathode is replaced by an Al Schottky contact the current varies exponentially with the applied voltage V. The current changes to space charge limited current (SCLC) at high voltages. The voltage at which the change takes place depends on the doping concentrations. In the SCLC regime the current varies according to the well-known V2 law if there are no traps and the mobility is independent of the electric field. If either trapping or effect of field on mobility is important, the current varies as Vm, where m>2. We have investigated experimentally the I–V characteristics of Schottky diodes fabricated using the PPV-based oligomer 2,5-di-n...

Matched pair of CoolMOST/sup TM/ transistor with SiC-Schottky diode-advantages in application

Abstract: The new CoolMOS C3 generation combines extremely high on-state conductivity with ultrafast switching speed at full pulse current capability. In the first generation of CoolMOS the saturation current was intentionally reduced at the cell level for the benefit of short-circuit ruggedness. This technique results in a reduced current capability of the device at low gate voltages, which has been overcome today by the C3 family. In some applications the outstanding switching performance of the CoolMOS cannot be utilized due to the dynamic behavior of the diode. For this reason a whole family of SiC diodes has been developed to attain the ideal matched pair of switch and ultrafast diodes. The goal of ultralow-loss applications in switched mode power supplies, power factor correction circuits, and motor control units will be achieved perfectly.

Trenched schottky rectifiers

Abstract: Inner trenches (11) of a trenched Schottky rectifier (1a; 1b; 1c; 1d) bound a plurality of rectifier areas (43a) where the Schottky electrode (3) forms a Schottky barrier 43 with a drift region (4). A perimeter trench (18) extends around the outer perimeter of the plurality of rectifier areas (43a). These trenches (11, 18) accommodate respective inner field-electrodes (31) and a perimeter field-electrode (38) that are connected to the Schottky electrode (3). The inner field-electrodes (11) are capacitively coupled to the drift region (4) via dielectric material (21) that lines the inner trenches (11). The perimeter field-electrode (38) is capacitively coupled across dielectric material (28) on the inside wall (18a) of the perimeter trench 18, without acting on any outside wall (18b). Furthermore, the inner and perimeter trenches (11, 18) are closely spaced and the intermediate areas (4a, 4b) of the drift region (4) are lowly doped. The spacing is so close and the doping is so low that the depletion layer (40) formed in the drift region (4), from the Schottky barrier (43) and from the field-relief regions (31,21; 38,28) in the blocking state of the rectifier, may deplete the whole of the intermediate areas (4a, 4b) between the trenches (11, 18) at a blocking voltage just below the breakdown voltage. This arrangement reduces the risk of premature breakdown that can occur at high field points in the depletion layer (40), especially at the perimeter of the array of rectifier areas (43a).

Lateral AlxGa1-xN power rectifiers with 9.7 kV reverse breakdown voltage

Abstract: AlxGa1−xN (x=0–0.25) Schottky rectifiers were fabricated in a lateral geometry employing p+-implanted guard rings and rectifying contact overlap onto an SiO2 passivation layer. The reverse breakdown voltage (VB) increased with the spacing between Schottky and ohmic metal contacts, reaching 9700 V for Al0.25Ga0.75N and 6350 V for GaN, respectively, for 100 μm gap spacing. Assuming lateral depletion, these values correspond to breakdown field strengths of ⩽9.67×105 V cm−1, which is roughly a factor of 20 lower than the theoretical maximum in bulk GaN. The figure of merit (VB)2/RON, where RON is the on-state resistance, was in the range 94–268 MW cm−2 for all the devices.

Design rules for field plate edge termination in SiC Schottky diodes

Abstract: Practical design of silicon carbide (SiC) Schottky diodes incorporating a field plate necessitates an understanding of how the addition of the field plate affects the performance parameters and the relationship between the diode structure and diode performance. In this paper, design rules are presented for SiC Schottky diodes that incorporate field plate edge termination. The use of an appropriate field plate edge termination can improve the reverse breakdown voltage of a SiC Schottky diode by a factor of two. Reverse breakdown voltage values can be obtained that are up to 88% of the theoretical maximums.

Vertical and lateral GaN rectifiers on free-standing GaN substrates

Abstract: Edge-terminated Schottky rectifiers fabricated on quasibulk GaN substrates showed a strong dependence of reverse breakdown voltage VB on contact dimension and on rectifier geometry (lateral versus vertical). For small diameter (75 μm) Schottky contacts, VB measured in the vertical geometry was ∼700 V, with an on-state resistance (RON) of 3 mΩ cm2, producing a figure-of-merit VB2/RON of 162.8 MW cm−2. Measured in the lateral geometry, these same rectifiers had VB of ∼250 V, RON of 1.7 mΩ cm2 and figure-of-merit 36.5 MW cm−2. The forward turn-on voltage (VF) was ∼1.8 V (defined at a current density of 100 A cm−2), producing VB/VF ratios of 139–389. In very large diameter (∼5 mm) rectifiers, VB dropped to ∼6 V, but forward currents up to 500 mA were obtained in dc measurements.

200, 400 and 800 GHz Schottky diode "substrateless" multipliers: design and results

Abstract: Several sub-millimeter doubler circuits have been designed and built using a new fabrication technology. To reduce the RF losses in the passive circuitry, the substrate under the transmission lines is etched away, leaving the metal suspended in air held by its edges on a GaAs frame. This allows the circuit to be handled and mounted easily, and makes it very robust. To demonstrate this technology, broadband balanced planar doublers have been built and tested at 400 GHz. The next generation 200, 400 and 800 GHz doublers with improved performance are also discussed. The 368-424 GHz circuits were measured and achieved 20% efficiency at 387 GHz. The 3 dB bandwidth of the fix-tuned doubler is around 9%. The maximum output power measured is around 8 mW and drops down to 1 mW at 417 GHz. This represents the highest frequency waveguide based planar doubler to date in the literature.

Trench schottky rectifier

Abstract: A Schottky rectifier is provided. The Schottky rectifier comprises: (a) a semiconductor region having first and second opposing faces, with the semiconductor region comprising a cathode region of first conductivity type adjacent the first face and a drift region of the first conductivity type adjacent the second face, and with the drift region having a lower net doping concentration than that of the cathode region; (b) one or more trenches extending from the second face into the semiconductor region and defining one or more mesas within the semiconductor region; (c) an insulating region adjacent the semiconductor region in lower portions of the trench; (d) and an anode electrode that is (i) adjacent to and forms a Schottky rectifying contact with the semiconductor at the second face, (ii) adjacent to and forms a Schottky rectifying contact with the semiconductor region within upper portions of the trench and (iii) adjacent to the insulating region within the lower portions of the trench.

Method concerning a junction barrier Schottky diode, such a diode and use thereof

Abstract: A method for controlling the temperature dependence of a junction barrier Schottky diode of a semiconductor material having an energy gap between the valence band and the conduction band exceeding 2 eV provides for doing this when producing the diode by adjusting the on-state resistance of the grid portion of the diode during the production for obtaining a temperature dependence of the operation of the diode adapted to the intended use thereof.

Junction properties of metal/polypyrrole Schottky barriers

Abstract: Schottky barriers of the type Au/polypyrrole/Al (or In) were made in sandwich configuration. The conductivity of polypyrrole was tuned to be on the order of 10−3 ohm−1 cm−1 by its electrodeposition from a novel ambient temperature ternary eutectic melt consisting of acetamide, urea, and ammonium nitrate. The rectification characteristics were obtained from the current–voltage and capacitance–voltage measurements at room temperature. The analysis of data using thermionic emission theory gave improved values for the junction parameters of ideality factor, reverse saturation current, rectification ratio, and barrier potential when compared to the previously reported values for this polymer. Between Al and In metals used for the junction formation, the diode formed with Al metal is found to show better performance. The energy gap and work function of polypyrrole were also estimated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2127–2135, 2001

Gate electrode formation in double-recessed transistor by two-step etching

Abstract: A transistor structure is provided. This structure has a source electrode and a drain electrode. A doped cap layer of GaxIn1−xAs is disposed below the source electrode and the drain electrode and provides a cap layer opening. An undoped resistive layer of GaxIn1−xAs is disposed below the cap layer and defines a resistive layer opening in registration with the cap layer opening and having a first width. A Schottky layer of AlyIn1−yAs is disposed below the resistive layer. An undoped channel layer is disposed below the Schottky layer. A semi-insulating substrate is disposed below the channel layer. A top surface of the Schottky layer beneath the resistive layer opening provides a recess having a second width smaller than the first width. A gate electrode is in contact with a bottom surface of the recess provided by the Schottky layer.

Hydrogen-sensitive characteristics of a novel Pd/InP MOS Schottky diode hydrogen sensor

Abstract: Steady-state and transient hydrogen-sensing characteristics of a novel Pd/InP metal-oxide-semiconductor (MOS) Schottky diode under atmospheric conditions are presented and studied. In presence of oxide layer, the significant increase of barrier height improves the hydrogen sensitivity even at lower operating temperatures. Even at a very low hydrogen concentration environment, e.g., 15 ppm H/sub 2/ in air, a significant response is obtained. Two effects, i.e., the removal of Fermi-level pinning caused by the donor level in the oxide and the reduction of Pd metal work function dominate the hydrogen sensing mechanism. Furthermore, the reaction kinetics incorporating the water formation upon hydrogen adsorption is investigated. The initial heat of adsorption for the Pd/oxide interface is estimated to be 0.42 eV/hydrogen atom. The coverage dependent heat of adsorption plays an important role in hydrogen response under steady-state conditions. In accordance with the Temkin isotherm behavior, the theoretical prediction of interface coverage agrees well with the experimental results over more than three decades of hydrogen partial pressure.