Showing papers on "Schottky diode published in 1992"

Optoelectronic measurement of semiconductor surfaces and interfaces with femtosecond optics

Abstract: The basic concepts and preliminary applications of optically induced electromagnetic radiation from semiconductor surfaces and interfaces by using femtosecond optics are discussed. This submillimeter‐wave radiation provides a novel optoelectronic technique to study semiconductor electronic surface and interface properties with a contactless approach. The amplitude and phase of the electromagnetic radiation from the semiconductor surfaces depend on carrier mobility, impurity doping concentration, and strength and polarity of the static internal field. A large selection of bulk, epitaxial layer and superlattice samples from III‐V, II‐VI and group‐IV semiconductors has been tested. The orientation and strength of the static built‐in fields of a wide range of semiconductor surfaces, such as surface depletion, metal/semiconductor Schottky, p‐n junction and strain‐induced piezoelectric fields, can be determined and estimated.

Silicon-carbide high-voltage (400 V) Schottky barrier diodes

Abstract: The authors describe the fabrication and characteristics of the first high-voltage (400-V) silicon-carbide (6H-SiC) Schottky barrier diodes. Measurements of the forward I-V characteristics of these diodes demonstrate a low forward voltage drop of approximately 1.1 V at an on-state current density of 100 A/cm/sup 2/ for a temperature range of 25 to 200 degrees C. The reverse I-V characteristics of these devices exhibit a sharp breakdown, with breakdown voltages exceeding 400 V at 25 degrees C. In addition, these diodes are shown to have superior reverse recovery characteristics when compared with high-speed silicon P-i-N rectifiers. >

Theoretical and experimental investigation of a rectenna element for microwave power transmission

Abstract: A method has been devised to experimentally characterize a packaged GaAs Schottky barrier diode by inserting it into a microstrip test mount. The nonlinear equivalent circuit parameters of the diode are determined by a small-signal test method. A large-signal measurement using the same test mount has also been configured to determine the power conversion efficiency from microwave to DC as well as determining the de-embedded network impedance of the diode. A nonlinear circuit simulation program using a multireflection algorithm is used to verify the experimental results for the 2.45-GHz diode. A Ka-band mixer diode is simulated for a 35-GHz rectenna. Based on the simulation results, a patch-type 35-GHz rectenna is designed and tested in a waveguide simulator. The efficiency is 29% with 120-mW input power. Because the diode could generate undesirable harmonic radiation, a frequency-selective surface is designed to reduce the second harmonic radiation for a 2.45-GHz rectenna. Theoretical results agree fairly well with experiments for all these studies. >

Parameter extraction from non-ideal C−V characteristics of a Schottky diode with and without interfacial layer

Abstract: In this study, we have attempted to interpret experimentally observed non-ideal AlpSi Schottky diode I-V and C−2−V characteristics which are due to an interface layer, interface states and fixed surface charge. A value of 0.68 eV for the barrier height qΦBo for AlpSi diodes without interface layer and fixed surface charge has been obtained from C−2−V characteristics and a value of 0.20 eV for the neutral level of the surface states has been found. Furthermore, the value of the barrier height qΦBp without fixed surface charge and the effective barrier height qΦBp,o are separately obtained from C−2-V characteristics. In addition, values of interface state density Dit have been calculated.

Current saturation in submillimeter-wave varactors

Abstract: In semiconductor devices the speed of electrons cannot exceed certain limits. This phenomenon will affect varactor multipliers as well as other high-frequency devices where the RF current through the active part of the device is primarily displacement current. Hence, at some point, 'saturation' of the varactor output power is expected. The authors discuss this phenomenon in some detail and show that it severely deteriorates the multiplier performance at higher frequencies. Single barrier varactors (SBVs) should have an advantage over GaAs Schottky diode varactors because they can be fabricated on InAs and stacked in a series array, allowing for lower current densities and higher power handling. >

Frequency multipliers for millimeter and submillimeter wavelengths

Abstract: Theory and tools for analysis and design of millimeter- and submillimeter-wave multipliers are discussed. Experimental work is reviewed. The Schottky diode model at submillimeter frequencies, use of Schottky multiplier chains versus direct higher-order multipliers, and the effect of cooling on Schottky diode multipliers are discussed. Alternative diodes such as the high electron mobility varactor (HEMV), the barrier-intrinsic-n/sup +/ diode (BIN), the barrier-n-n/sup +/ diode (BNN), the quantum well diode (QWD), and the single barrier varactor (SBV) are discussed, with attention given to their potential submillimeter frequency multipliers. >

High power, high frequency metal-semiconductor field-effect transistor formed in silicon carbide

Abstract: A high power, high frequency, metal-semiconductor field-effect transistor comprises a bulk single crystal silicon carbide substrate, an optional first epitaxial layer of p-type conductivity silicon carbide formed upon the substrate, and a second epitaxial layer of n-type conductivity silicon carbide formed upon the first epitaxial layer. The second epitaxial layer has two separate well regions therein that are respectively defined by higher carrier concentrations of n-type dopant ions than are present in the remainder of the second epitaxial layer. Ohmic contacts are positioned upon the wells for respectively defining one of the well regions as the source and the other as the drain. A Schottky metal contact is positioned upon a portion of the second epitaxial layer that is between the ohmic contacts and thereby between the source and drain for forming an active channel in the second epitaxial layer when a bias is applied to the Schottky contact.

Submillimeter receivers for radio astronomy

Abstract: The state of development of receivers for submillimeter-wave radio astronomy is reviewed. Bolometers for continuum observation, hot-electron mixer receivers for narrowband spectral line observation, and heterodyne receivers, both Schottky diode and superconducting tunnel junction, are presented. At the lower frequency end of the submillimeter band, standard waveguide techniques, scaled from millimeter wavelengths, prevail. At wavelengths shorter than about 0.5 mm, quasioptical designs are preferred. In the case of Schottky diode receivers, corner cube designs are used almost exclusively, whereas integrated mixer designs are the focal point of research for superconductor-insulator-superconductor (SIS) receivers at these wavelengths. Although such designs are extensively reviewed, it is nevertheless the Schottky diode mixer remains the element of choice at the shortest submillimeter wavelengths. >

GaAs Schottky diodes for THz mixing applications

Abstract: The operation of GaAs Schottky barrier diodes, the critical mixer element used in heterodyne receivers for a variety of scientific applications in the terahertz frequency range, is reviewed. The constraints that the receiver system places on the diodes are considered, and the fundamental guidelines for device optimization are presented. The status of ongoing research, both experimental and theoretical, is examined. Emphasis is placed on investigations of the various effects that can limit diode performance at these high frequencies. Investigations of planar diode technology are summarized, and the potential replacement of whisker-contacted devices with planar structures is considered. >

Photovoltaic output limitation of n‐FeS2 (pyrite) Schottky barriers: A temperature‐dependent characterization

Abstract: Metal/n‐pyrite (metal=Pt, Au, Nb) Schottky barrier type diodes were fabricated on electrochemically reduced either synthetic or natural (100) and (111) surfaces of single crystalline n‐FeS2. The temperature dependence of I‐V curves in darkness were analyzed in the range of 200–350 K on the basis of thermionic emission and recombination models. The calculated effective barrier height was ∼0.60 eV and the activation energy for recombination ∼0.50 eV for all investigated n‐FeS2/Pt samples. The doping density and the extrapolated potential (pseudo flatband situation) from the Mott–Schottky plot, obtained from capacities deduced from potentiostatic complex impedance measurements, were 2.0×1016 cm−3 and 0.25 eV vs Pt for the synthetic n‐pyrite crystal, respectively. From the donor density and barrier height a band bending of 0.5 eV was deduced. Photovoltaic parameters like open‐circuit photovoltage and short‐circuit photocurrent were studied down to temperatures of 200 K. The main phenomenon preventing the gene...

On the inhomogeneity of Schottky barriers

Abstract: It is shown that the wide diversity of behavior observed from common Schottky barriers is difficult to reconcile with the traditional view of a homogeneous barrier height which is determined by Fermi level pinning, but is consistent with the presence of inhomogeneities in the barrier height. The demonstrated inhomogeneity in Schottky barriers, which is shown to have a dominant effect on electron transport, is suggestive of a dependence on the barrier height on the interface structure. Experimental and theoretical results obtained from high-quality epitaxial Schottky junctions are also discussed to show the correlation between the interface structure and the barrier height.

Interfacial reactions and Schottky barriers of Pt and Pd on epitaxial Si1-xGex alloys

Abstract: The evolution of interfacial reactions during the deposition of Pt and Pd on epitaxial Si1−xGex alloys was studied using x‐ray photoelectron spectroscopy (XPS) for metal coverage up to 10 A. Auger electron depth profiling was performed on a thicker metal overlayer before and after in vacuo annealing to study the redistribution of composition in the reactions. We have found that Pt and Pd react mainly with Si to form silicides at 350 °C, leaving some Ge to segregate at the surface. These results were correlated with Schottky barrier height measurements. We found that the Schottky barrier heights of Pt/n‐Si0.8Ge0.2 and Pd/n‐Si0.8Ge0.2 are about the same, pinned at 0.68 eV, which is much smaller than those of n‐Si. These barrier heights are quite stable up to 550 °C.

Improved ohmic contacts for p-type ZnSe and related p-on-n diode structures

Abstract: The problem of obtaining ohmic contacts for p‐type ZnSe is related to the deep valence band of ZnSe. We have addressed this problem by employing an epitaxial layer of the semimetal HgSe to decrease the interfacial energy barrier, or valence band offset, to about 0.6 eV. This has resulted in improved ohmic contacts for p‐type ZnSe films and related diode structures.

A 15 element focal plane array for 100 GHz

Abstract: A focal plane imaging array receiver is described which covers the 86-115 GHz frequency range for radio astronomical observations. The 3*5 element array uses cryogenic Schottky diode mixers with integrated HEMT IF amplifiers. A cold quasi-optical filter selects the desired sideband, and terminates the image at 20 K. Polarization interleaving is used to minimize the array size on the sky. LO power is provided by a frequency tripled YIG tuned oscillator. The average receiver noise temperature of the array pixels varies from 250-350 K SSB depending on the frequency. Only three mechanical tuners are used in the system and all functions are under computer control. >

Confinement and single-electron tunneling in Schottky-gated, laterally squeezed double-barrier quantum-well heterostructures.

Abstract: The conductance of laterally confined double-barrier quantum-well resonant-tunneling heterostructures is investigated. The confinement is provided by a Schottky gate and can be varied in a continuous way, giving direct proof of the quantum size effect. Data for dots with nominal diameters in the submicron range are reported. Possible evidence for a modulation of the Coulomb blockade by quantum confinement is presented

Semiconductive polymer‐based Schottky diode

Abstract: Polythiophene is easily obtained electrochemically on a Au surface in an acetonitrile/0.25 M LiClO4 solution. On the basis of this knowledge, we prepared a metal‐semiconductor‐metal Schottky diode, in which Au and Al were used as metals and freshly prepared polythiophene as a semiconductor. Current‐voltage and capacity‐voltage characteristics of this diode have been obtained under atmospheric conditions.

A novel Schottky/2-DEG diode for millimeter- and submillimeter-wave multiplier applications

Abstract: A high-frequency diode is proposed for use as a frequency multiplier element in the millimeter- and submillimeter-wavelength regions. The Schottky/2-DEG diode utilizes a Schottky contact along the edge of a two-dimensional electron gas (2-DEG) structure. This geometry allows one to combine a very low series resistance due to the excellent transport properties of the 2-DEG with a high breakdown voltage caused by the 2-D electric field spreading in the depletion region (compared to a 1-D field variation in the conventional Schottky diode). The higher Fermi velocity of the 2-DEG leads to a less severe transit-time limitation of the frequency response. >

Midgap states in a‐Si:H and a‐SiGe:H p‐i‐n solar cells and Schottky junctions by capacitance techniques

Abstract: The midgap density of states (MGDOS) in a‐SiGe:H alloys is investigated by capacitance measurements on p‐i‐n solar cells. Past work on thick a‐Si:H Schottky barriers is extended to thin a‐SiGe:H p‐i‐n cells. Four methods of determining the MGDOS from the measured capacitance are described, and each is applied to two p‐i‐n devices having 0% and 62% Ge in the i layers, respectively. The first method involves fitting an equivalent circuit model to the measured admittance. Close agreement is found over a wide range of temperature and frequency. The single junction model is shown to apply equally well to p‐i‐n and Schottky diodes, justifying the neglect of the n‐i junction and thin doped layers in the p‐i‐n admittance analysis. A second method determines g0 from the limiting capacitance at high temperature. The third and fourth methods extract g0 from the dependence of capacitance on voltage bias. One of these is novel, presented here for the first time. Thus, a unique feature of this study is the application ...

Vacuum‐deposited metal/polyaniline Schottky device

Abstract: All vacuum‐deposited metal/semiconducting polyaniline hetrojunction Schottky devices using vacuum‐evaporated polyaniline films of a thickness of the order of 0.1 μm have been prepared. Schottky junctions have been formed using the following metals, Al, Sn, In, Pb, Sb, and Ag. Electrical characterization has been carried out and electronic parameters, including the barrier height and ideality factor, have been determined. Infrared optical absorption spectroscopy of the vacuum‐deposited polyaniline films were used to determine the structure, energy band gap, and effect of various ambients on the vacuum‐deposited polyaniline films.

Determination of the density of Si-metal interface states and excess capacitance caused by them

Abstract: Schottky diodes were fabricated by evaporation of Al on a strongly etched n-type Si surface for 3 min after mechanical cleaning. The measurements of one of the better working of the Al-nSi diodes has been carried out at room temperature. Two expressions were found for the ideality factor n by supposing that all the interface states at first are in equilibrium with the metal and then with the semiconductor. The diode showed non-ideal I–V behaviour with an ideality factor of 1.46. The density distribution of interface states was obtained from the forward bias I–V characteristics. Non-linearity or curvature in the reverse bias C -2 − V plots was a quantity called the “excess capacitance” C 0 caused by the presence of the interface states. The excess capacitance was observed to decrease with increasing frequency: this behaviour was ascribed to the fact that the apparent density of the interface states decreases with increasing frequency. In addition, the parameters obtained from C − V characteristics were corrected by means of a simple graphical method for excess capacitance suggested by Vasudev et al. and of a theoretical model of an MIS structure introduced by Fonash.

Multiple sequential excitation temperature sensing method and apparatus

Abstract: The temperature at a semiconductor device having a generally non-linear, temperature dependent relationship between a pair of device parameters is determined by applying a plurality of sequential excitations to the device at different excitation levels, sensing the levels of the device parameters that correspond to the sequential excitations, and determining the device temperature from the sequential device parameter levels. The device may include a p-n junction, and is preferably a bipolar transistor whose collector current and base-emitter voltage serve as the parameters from which the temperature is obtained. Using three sequential excitations, an accurate temperature reading can be obtained that substantially cancels the effects of the transistor's parasitic base and emitter resistances. p-n junction diodes and Schottky diodes may also serve as the device, in which case the current through and voltage across the diode are used to determine temperature.

Process for the simultaneous fabrication of high-and-low-voltage semiconductor devices, integrated circuit containing the same, systems and methods

Abstract: An integrated process is shown for the fabrication of one or more of the following devices: (n-) and (p-) channel low-voltage field-effect logic transistors (139/140); (n-) and (p-) channel high-voltage insulated-gate field-effect transistors (141, 142) for the gating of an EEPROM memory array or the like; a Fowler-Nordheim tunneling EEPROM cell (143); (n-) and (p-) channel drain-extended insulated-gate field-effect transistors (144, 145); vertical and lateral annular DMOS transistors (146, 147); a Schottky diode (148); and a FAMOS EPROM cell (149). A "non-stack" double-level poly EEPROM cell (676) with enhanced reliability (676) is also disclosed.

Electrically programmable antifuse using metal penetration of a junction

Abstract: An improved antifuse uses metal penetration of either a P-N PN junction or a Schottky diode. The P-N junction or Schottky diode (11), is contacted by a diffusion barrier (14) such as TiN, W, Ti-W alloy, or layers of Ti and Cr, with a layer (15) of a metal such as Al, Al-Cu alloy, Cu, Au, or Ag on top of the diffusion barrier. The junction (11) is surrounded by an electrical isolation structure (13) which also serves to thermally isolate the said junction. When this junction is stressed with voltage pulse producing a high current density, severe joule heating occurs resulting in metal penetration of the diffusion barrier and the junction to form a metal contact (15'). The voltage drop across the junction decreases by about a factor of ten after the current stress and is stable thereafter. Alternatively, a shallow P-N junction in a silicon substrate is contacted by a layer of metal that forms a silicide, such as Ti, Cr, W, Mo, or Ta. Stressing the junction with a voltage pulse to produce a high current density results in the metal penetrating the junction and reacting with the substrate to form a silicide.

Schottky barrier height enhancement on n‐In0.53Ga0.47As

Abstract: Schottky barrier height enhancement on n‐InGaAs is studied on structures with thin surface layers of different compositions. Counter‐doped p+‐InGaAs layers, as well as layers of n‐ and p‐InP, n‐GaAs, and n‐InGaP of different thicknesses and dopant densities, respectively, were used to enhance the barrier. Titanium was used as a barrier metal to prepare Schottky diodes of different areas and the barrier height is analyzed by current‐voltage measurements. It is observed that the barrier height enhancement by p+‐InGaAs layers increases with the layer thickness and dopant density, respectively, and effective barrier heights up to 0.63–0.68 eV, i.e., higher values than previously reported, have been measured. The barrier height enhancement by counter‐doped p+‐InGaAs layers on n‐InGaAs can be described by the two‐carrier model. Schottky diodes with extremely low reverse current densities have been prepared, JR(1 V) =4.5×10−6 A/cm2. It is shown that lattice‐matched InP surface layers can be used as an alternativ...

A systematic approach to the measurement of ideality factor, series resistance, and barrier height for Schottky diodes

Abstract: A nongraphical approach is proposed for measuring and evaluating the ideality n factor and the series resistance of a Schottky diode. The approach involves the use of an auxiliary function and a computer‐fitting routine. This technique has been found to be both accurate and reliable. The validity of this has also been confirmed by way of I‐V measurements using both commercially available and laboratory‐prepared Schottky diodes.

Ideal Schottky diodes on passivated silicon

Abstract: Because of the complicated electronic and metallurgical properties of the metal-semiconductor interface, there is much controversy about the theoretical interpretation of experimental results on Schottky barrier heights. We present a new approch of barrier height measurements on a prototypical clean, abrupt and noninteracting system consisting of mercury contacts to hydrogen-passivated silicon surfaces. The resulting barrier to p-silicon is 0.9 V, totally at variance with all results presented for silicon Schottky barriers fabricated by standard metal deposition techniques. We believe this to be the first report in the limit of noninteracting metal contacts to silicon.

Simple interface-layer model for the nonideal characteristics of the Schottky-barrier diode

Abstract: Interface states may affect the voltage-capacitance characteristics of metal-semiconductor junctions causing a bending of the (measured) I C 2 vs reverse bias. This nonideal plot can be transformed into a linear C vs (V 0 − V) − 1 2 plot making possible extraction of some interface parameters.

Properties of the planar poly(3‐octylthiophene)/aluminum Schottky barrier diode

Abstract: Formation and characterization of planar polymer Schottky barrier diodes are presented. Electrical characteristics of planar aluminium‐poly(3‐octylthiophene) Schottky barrier diodes are studied with emphasis on the current transport mechanisms. The device exhibits nearly ideal diode behavior in dark with an ideality factor of n=1.2. Temperature dependence of the current‐voltage characteristics of the diode is studied in the range 170–370 K. Agreement with the diffusion theory of metal‐semiconductor rectification is demonstrated for high temperatures T≳300 K. For temperatures less than room temperatures tunneling is proposed to be the dominant current transport mechanism.