Showing papers on "Schottky diode published in 1991"

Visible light emission from semiconducting polymer diodes

Abstract: We report visible light emission from Shottky diodes made from semiconducting polymers, confirming the discovery by the Cambridge group [Nature 347, 539 (1990)]. Our results demonstrate that light‐emitting diodes can be fabricated by casting the polymer film from solution with no subsequent processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 104. We propose that tunneling of electrons from the recitifying metal contact into the gap states of the positive polaron majority carriers dominates current flow and provides the mechanism for light emission.

Barrier inhomogeneities at Schottky contacts

Abstract: We present a new analytical potential fluctuations model for the interpretation of current/voltage and capacitance/voltage measurements on spatially inhomogeneous Schottky contacts. A new evaluation schema of current and capacitance barriers permits a quantitative analysis of spatially distributed Schottky barriers. In addition, our analysis shows also that the ideality coefficient n of abrupt Schottky contacts reflects the deformation of the barrier distribution under applied bias; a general temperature dependence for the ideality n is predicted. Our model offers a solution for the so‐called T0 problem. Not only our own measurements on PtSi/Si diodes, but also previously published ideality data for Schottky diodes on Si, GaAs, and InP agree with our theory.

Electron transport of inhomogeneous Schottky barriers: A numerical study

Abstract: Numerical simulations are presented of the potential distribution and current transport associated with metal‐semiconductor (MS) contacts in which the Schottky barrier height (SBH) varies spatially. It is shown that the current across the MS contact may be greatly influenced by the existence of SBH inhomogeneity. Numerical simulations indicate that regions of low SBH are often pinched‐off when the size of these regions is less than the average depletion width. Saddle points in the potential contours in close proximity to the low‐SBH regions, which are shown to vary with the dimension and magnitude of the inhomogeneity as well as with bias, essentially determine the electron transport across the low‐SBH regions. It is these dependences of the saddle point which give rise to various abnormal behaviors frequently observed from SBH experiments, such as ideality factors greater than unity, various temperature dependences of the ideality factor, including the T 0 anomaly, and reverse characteristics which are strongly bias‐dependent. The results of these numerical simulations are shown to support the predictions of a recently developed analytic theory of SBH inhomogeneity.

Thin film deposition and microelectronic and optoelectronic device fabrication and characterization in monocrystalline alpha and beta silicon carbide

Abstract: The deposition of silicon carbide thin films and the associated technologies of impurity incorporation, etching, surface chemistry, and electrical contacts for fabrication of solid-state devices capable of operation at temperatures to 925 K are addressed. The results of several research programs in the United States, Japan and the Soviet Union, and the remaining challenges related to the development of silicon carbide for microelectronics are presented and discussed. It is concluded that the combination of alpha -SiC on alpha -SiC appears especially viable for device fabrication. In addition, considerable progress in the understanding of the surface science, ohmic and Schottky contacts, and dry etching have recently been made. The combination of these advances has allowed continual improvement in Schottky diode p-n junction, MESFET, MOSFET, HBT, and LED devices. >

Electron transport of inhomogeneous schottky barriers

Abstract: A novel approach is presented which leads to analytic solutions to the potential and the electron transport through inhomogeneous Schottky barriers The existence of barrier height nonuniformities is shown to provide a simple explanation of the following abnormal experimental results, routinely observed from various Schottky barriers: greater‐than‐unity ideality factors, the T0 effect, the ‘‘soft’’ reverse characteristics, and the dependence of barrier height on the technique of measurement

GaAs nonlinear transmission lines for picosecond pulse generation and millimeter-wave sampling

Abstract: The GaAs nonlinear transmission line (NLTL) is a monolithic millimeter-wave integrated circuit consisting of a high-impedance transmission line loaded by reverse-biased Schottky contacts. The engineering of functional monolithic NLTLs is considered. Through generation of shock waves on the NLTL, the authors have generated electrical step functions with approximately 5 V magnitude and less than 1.4 ps fall time. Diode sampling bridges strobed by NLTL shock-wave generators have attained bandwidths approaching 300 GHz and have applications in instruments for millimeter-wave waveform and network measurements. The authors discuss the circuit design and diode design requirements for picosecond NLTL shock-wave generators and NLTL-driven sampling circuits. >

The electrical properties and device applications of homoepitaxial and polycrystalline diamond films

Abstract: Electronic applications of semiconductor diamonds are addressed. Doping and electrical properties of these films, formation of low-resistive 'ohmic' contacts, surface modification methods, and experimental device applications are discussed. Of particular interest are high-temperature (300 degrees C) MOSFETs and metal contacts to CVD (chemical vapor deposition) diamond films which were used to fabricate high-temperature (580 degrees C) Schottky diodes, rudimentary MESFETs, and blue light-emitting diodes (LEDs). The status of the emerging technology is reviewed with an emphasis on the areas of current research activity. >

Analysis of I-V measurements on PtSi-Si Schottky structures in a wide temperature range

Abstract: I–V Measurements on PtSi-Si Schottky structures in a wide temperature range from 90 to 350 K were carried out. The contributions of thermionic-emission current and various other current-transport mechanisms were assumed when evaluating the Schottky barrier height Φ0. Thus the generation-recombination, tunneling and leak currents caused by inhomogeneities and defects at the metal-semiconductor interface were taken into account. Taking the above-mentioned mechanisms and their temperature dependence into consideration in the Schottky diode model, an outstanding agreement between theory and experiment was achieved in a wide temperature range. Excluding the secondary current-transport mechanisms from the total current, a more exact value of the thermionic-emission saturation current Ite and thus a more accurate value ofΦb was reached. The barrier height Φb and the modified Richardson constant A∗∗ were calculated from the plot of thermionic-emission saturation current Ite as a function of temperature too. The proposed method of finding Φb is independent of the exact values of the metal-semiconductor contact area A and of the modified Richardson constant A∗∗. This fact can be used for determination of Φb in new Schottky structures based on multicomponent semiconductor materials. Using the experimentally evaluated value A∗∗ = 1.796 × 106Am−2K−2 for the barrier height determination from I–V characteristics the value of Φb = 0.881 ± 0.002 eV was reached independent of temperature. The more exact value of barrier height Φb is a relevant input parameter for Schottky diode computer-aided modeling and simulation, which provided a closer correlation between the experimental and theoretical characteristics.

Metal/semiconductive polymer Schottky device

Abstract: Development of a metal/organic‐semiconductor Schottky junction as an alternative to the metal/inorganic‐semiconductor junction is reported. Metal/polypyrrole (PP) junctions have been prepared with electrochemically deposited doped PP films of different thickness and various metals (In, Sn, Ti, and Al) as electrodes. The electrical characteristics of the junction depend upon the work functions of PP and the metal. It has been possible to prepare Schottky barriers on the PP films with a metal electrode having a work function lower than that of the polymer. Various physical characteristics of the polymer, work function, Fermi level, and carrier concentration have been estimated.

Ion beam synthesis of buried α-FeSi2 and β-FeSi2 layers

Abstract: Using high dose implantation of Fe+ into (111)Si, followed by rapid thermal annealing (RTA) at 1150 °C for 10 s, we fabricated continuous buried layers of the metallic α‐FeSi2 phase. Rutherford backscattering experiments indicate that these layers contain a large number of Fe vacancies, up to 18%. By implanting through a SiO2 mask, we produced Schottky diodes with idealty factors of 1.4±0.1 and a Schottky barrier height of ΦB=0.84±0.03 eV on (111) n‐Si. In this letter we report for the first time the formation of the semiconducting stoichiometric FeSi2 (β‐FeSi2) phase by annealing the buried α‐FeSi2 layers below the phase transition temperature of 937 °C; specifically at 750 °C for 20 h.

Properties of the Organic‐on‐Inorganic Semiconductor Barrier Contact Diodes In/PTCDI/p‐Si and Ag/CuPc/p‐Si

Abstract: The properties are discussed of organic-on-inorganic (OI) semiconductor contact barrier diodes, where the 3, 4, 9, 10 perylenetetracarboxylic diimide (PTCDI) and the copper phthalocyanine (CuPc) serve as the organic thin film. The results presented can be fully understood in terms of the thermionic emission-space-charge-limited (TE-SCL) current model introduced for OI structures with prototypical aromatic compound; 3, 4, 9, 10 perylenetetracarboxylic dianhydride (PTCDA) vapour-deposited onto n- and p-Si substrates. Also, under moderate and high reverse bias voltages the results obtained can be understood in terms of the organic-on-inorganic heterojunction (OI-HJ) model. Comparisons between diode performances and theory are made. The contact barrier diodes exhibit high breakdown voltages and reverse dark currents limited by generation and recombination of carriers in the Si bulk. From the forward current-voltage characteristics at several temperatures, apparent OI contact barriers of Φbp = (0.63 ± 0.01) V for PTCDI and Φbp = (0.59 ± 0.02) V for CuPc, are formed with p-Si substrates. Studies of the I–U characteristics suggest the presence of an exponential trap distribution in the band-gap of the organic semiconductors used. The resulting diodes are superior in many respect to conventional Schottky diodes due to enhanced contact barriers and reduced edge effects.

Picosecond pulse response characteristics of GaAs metal‐semiconductor‐metal photodetectors

Abstract: We present a comprehensive theoretical and experimental analysis of the current response of GaAs metal‐semiconductor‐metal Schottky photodiodes exposed to 70 fs optical pulses. Theoretical simulations of the carrier transport in these structures by a self‐consistent two‐dimensional Monte Carlo calculation reveal the strong influence of the distance between the finger electrodes, the external voltage, the GaAs layer thickness and the excitation intensity on the response time and the corresponding frequency bandwidth of these photodetectors. For many experimental conditions, the model demonstrates a clear temporal separation of the electron and hole contributions to the output current due to the different mobilities of the two carrier types. For a diode with an electrode separation of 0.5 μm, an electric‐field strength above 10 kV/cm and low intensity of the incident light the theory predicts a pulse rise time below 2 ps, an initial rapid decay as short as 5 ps associated with the electron sweep out and a s...

A new method to fabricate Au/n-type InP Schottky contacts with an interfacial layer

Abstract: A method to fabricate Au- n -type InP Schottky contacts with an interfacial layer has been developed. The interfacial layer is formed by deposition of a P x O y layer and reaction of this layer with the InP substrate. The current-voltage and capacitance-voltage characteristics are measured at various temperatures. Excellent rectification is found in the fabricated contacts. The observed reverse currents are very low. The ideality factors are around 1.15. Apparent barrier heights qφ B are evaluated from the extrapolated forward saturation current I s . They are found to be sufficiently high. The typical value of qφ B at room temperature is obtained as 0.88 eV. The Richardson plot ln( I s / T 2 ) vs 1/ T is well fitted in a straight line, where T is the temperature. From the Richardson plot, the true barrier height is estimated to be 0.41 eV. The effects of the interfacial layer are also discussed.

Enhancement of quantum efficiency in thin photodiodes through absorptive resonance

Abstract: The spectral response of resonantly enhanced photodiodes is analyzed theoretically and verified experimentally. Comprehensive design guidelines and formulas are given for device structures containing a metal reflector, a contact layer, and optional grading layer, an absorbing layer, and a quarter-wave stack (QWS). The analysis shows, for instance, that the quantum efficiency of a Schottky photodiode with a 162-nm GaInAs absorbing layer can be enhanced 3.7-fold by using a 41-layer AlInAs/AlGaInAs QWS. The number of layers required could be much lower for other material systems and/or if the substrate is removed. Experimentally, 50% enhancement is demonstrated for a 475-nm-thick absorbing layer at 1.52 mu m by using a 16-layer QWS. The resonance width is approximately 4.4%. >

Power vdmosfet with schottky on lightly doped drain of lateral driver fet

Abstract: A monolithic semiconductor device comprises a VDMOS transistor having first and second main electrodes and a control electrode, and a lateral MOSFET having first and second main electrodes and a control electrode, wherein one of the first and second electrodes of the lateral MOSFET has a lower doping concentration than that of the first and second main electrodes of the VDMOS transistor for forming a Schottky barrier diode.

High‐barrier height Schottky diodes on N‐InP by deposition on cooled substrates

Abstract: Ultrahigh barrier height (φB=0.96 eV) Schottky contacts to n‐InP, without an intentionally grown interficial oxide, were formed using metal deposition on a substrate cooled to as low as 77 K [low temperature (LT)]. φB = 0.46–0.52 eV for diodes deposited at room temperature (RT=300 K) agree well with previously published results, and give an ideality factor near unity. For the diodes deposited at LT=77 K, the leakage current density (J0) was reduced by more than 6–7 orders of magnitude with respect to the RT diodes. The φB for the LT diodes was increased from 0.48 to 0.96 eV for Pd metal and from 0.51 to 0.85 eV for Au metal, respectively. An alteration of the metal‐induced interface states, inhibition of surface segregation of the released In and P atoms, and very uniform metal coverage may be responsible for the distinct differences between the RT and LT diodes.

Conduction mechanism in PtSi/Si Schottky diodes.

Abstract: The conduction mechanism in PtSi/Si Schottky diodes has been studied in the temperature range of 80 to 300 K. Above 100 K the forward current-voltage (I-V) characteristic of the diodes is highly ideal and obeys the thermionic-emission theory including image-force lowering of the barrier. Certain diodes show a deviation from this behavior, which is due to carrier recombination in the depletion region. Factors that contribute to carrier recombination are a small area-to-periphery ratio and a thick silicide layer. Carrier recombination is also responsible for the soft behavior of the reverse I-V characteristic. The temperature dependence of the barrier height and the bias-independent position of the quasi-Fermi-level at the interface are shown to be associated with a high density of interface states. The activation energy found for the current transport at low temperatures suggests that these states are due to substitutional Pt atoms on the Si lattice.

Transport Properties of Inhomogeneous Schottky Contacts

Abstract: We review an analytical model for the interpretation of transport measurements on spatially inhomogeneous Schottky contacts. The comparison of barriers from current/voltage- as well as from capacitance/voltage-curves permits a quantitative analysis of spatially distributed Schottky barriers. We reveal that the ideality coefficient n of abrupt Schottky contacts reflects the deformation of the barrier distribution under applied bias; a general temperature dependence for the ideality n is predicted and observed. An extension of our model includes the so-called flat band barrier of current/voltage curves. Here we demonstrate the interdependence of flat band Schottky barrier, ideality n and the homogenization of the barrier distribution under the application of a bias voltage. Effective photoresponse barriers and electrical noise at inhomogeneous Schottky diodes are also discussed.

A New Hydrogen Sensor Based on a Pt / GaAs Schottky Diode

Abstract: A new hydrogen-sensitive detector based oii a PffGaAs Scliottlry diode has been fabricated. The dcvices have been characterized 'sy dark current-voltage aiid capacitance-voltage measurtrnents, as a function of temperature and gas phase composition. At 150°C, the detection limit for liydrogen is 6 ppm iil a nitrogeii environment and 200 ppm in air.

Barrier height change in GaAs Schottky diodes induced by piezoelectric effect

Abstract: A novel manifestation of piezoelectric effects in GaAs has been observed. The change of barrier height, φB, of Schottky diodes induced by uniaxial stresses, S, along 〈100〉, 〈011〉, 〈011〉, and 〈111〉 has been measured. Shifts in φB due to the appearance of piezoelectric polarization charges at the semiconductor‐metal interface for directions other than 〈100〉 are observed.

Schottky barrier heights of n-type and p-type Al/sub 0.48/In/sub 0.52/As

Abstract: The authors report electrical measurements on four different metal contacts which formed Schottky barriers to lightly doped complementary n- and p-type Al/sub 0.48/In/sub 0.52/As epitaxial material grown by molecular beam epitaxy on semi-insulating InP substrates. The Schottky contact metals studied were Au, Al, Pt, and tri-layer Ti/Pt/Au. The Schottky barrier heights varied from 0.560 eV for Al on n-type AlInAs to 0.905 eV for Al on p-type AlInAs, with intermediate values for the other metals studied. The sum of n- and p-type Schottky barrier heights for each metal contact ranged from 1.440 to 1.465 eV, in good agreement with the accepted Al/sub 0.48/In/sub 0.52/As bandgap value of 1.45 eV. >

On the Richardson constant for aluminum/gallium arsenide Schottky diodes

Abstract: Measurements have been made of the Richardson constant (A**) for Al/GaAs Schottky diodes in which the aluminum is deposited epitaxially by molecular beam epitaxy. These diodes are the nearest to ideal that have yet been reported. The value of (A**) for n‐type GaAs, after allowing for the temperature variation of the barrier height and for the effect of tunnelling, was found to be (0.41±0.15)×104 A m −2 K−2. This is much lower than the previously accepted value, and confirms the low value reported by Srivastava, Arora, and Guha. Since there is no possibility of an interfacial layer in our diodes, we believe the low value of A** to be an intrinsic property of the Al/GaAs interface. The value of A** for Al/p‐GaAs was found to be (7.0±1.5)×104 A m−2 K−2, which is lower than the theoretical value, though the discrepancy is not so large as for n‐type GaAs. Because of the uncertainty in A**, values of barrier hights obtained from C−2 vs V plots are likely to be more reliable than those deduced from I/V character...

Electrical Characterization of the Silicon‐Electrolyte Interface in the Conditions of Porous Silicon Formation

Abstract: A detailed experimental investigation of the electrical behavior of the silicon-electrolyte interface is presented, which leads to the conclusion that electrochemical dissolution of p-type silicon (doping range 10 15 cm −3 -3×10 19 cm −3 ) during porous silicon formation is mainly determined by the charge exchange at the silicon surface over the Schottky barrier formed at the interface through a thermoionic emission process. Impedance characterization of the interface allows the determination of the potential barrier formed between p-silicon and hydrofluoric acid solutions, and analysis of I(V) characteristics shows that the silicon-electrolyte junction behaves like a Schottky diode, with a particular dependence of the anodization potential vs. silicon doping which results from the voltage drop in the Helmholtz layer

Hemt structure with passivated donor layer

Abstract: A channel layer, donor layer, Schottky layer, and cap layer are formed on a substrate. A source and drain are formed on the cap layer. A gate is formed on the cap layer, or at the bottom of a recess which is formed through the cap layer and partially extends into the Schottky layer. The donor and Schottky layers are formed of a semiconductive material which includes an oxidizable component such as aluminum. A passivation or stop layer of a lattice-matched, non-oxidizable material is formed underlying the source, drain, and gate, and sealingly overlying the donor layer. The stop layer may be formed between the Schottky layer and the donor layer, or constitute a superlattice in combination with the Schottky layer consisting of alternating stop and Schottky sublayers. Alternatively, the stop layer may sealingly overlie the Schottky layer, and further constitute the cap layer.

Principles and technology of MODFETs

Abstract: Part 6 Measurements of transport properties of modulation doped heterostructures: Hall effect measurements interpretation of Hall measurements experimental Hall mobilities in (AI, Ga) As/GaAs MDHs - single interface structures, multiple interface structures experimental 2DEG density in AI,Ga) As/GaAs MDHs influences of substrate temperature on transport properties - ternary on top of binary - normal structures, binary on top of ternary - inverted structures the Dx centre effects in (AI, Ga) As/GaAs MDHs (AI,Ga) As/(In,Ga) As and (In,AI) As/(in,Ga)As MDHs high field electron mobility in MDHs high field electron volocity in MDHs - theoretical determination, experimental measurements. Part 7 Non-equilibrium characteristics of modulation loped fets: charge - voltage characteristics current - voltage (I-V) characteristics - normal regime, parallel conduction in the barier layer comparison with experimental I-V characteristics capacitance - voltage characteristics quasi-fermi level bending and its effect on Fet characteristics charge - voltage characteristics for invected modfets anomalies at low temperature (In,Ga) As/ (AI,Ga) as Modfet performance optimization enhanced Schottky barrier for Modfets. Part 8 Microwave characteristics of Modfets: device performance microwave modeling - small-signal model, large-signal model wave equation model - derivation of the wave-equation, solution of the wave equation, Y-parameter calculations, extraction of parameters needed for the AC model, comparison of the measured and calculated data, limitations of the microwave model noise modelling - the DC Fet model, Fet noise modeling, optimization of device parameters, evaluation of noise figures versus frequency, noise temperature. Part 9 Digital integrated circuits: basic inverters GaAs circuits - direct-coupled Fet logic (DCFL), buffered Fet logic (BFC), Schottky diode Fet logic (SDFL), source-coupled Fet logic (SCFL) modfet digital integrated circuits design and simulation of Modfet ICs - precursor logic circuits, comparator circuits, static-random access memory (SRAM) circuits, gate arrays short-channel effects radiation effects - radiation hardness of Modfest, radiation hardness of Modfet inverters and ring oscillators comparison with other technologies - ring oscillators, frequency divider, static random access memory (SRAM), projections.

Barrier height variation in Al/GaAs Schottky diodes with a thin silicon interfacial layer

Abstract: Al/n‐GaAs and Al/Si/n‐GaAs structures with thin silicon interfacial layers were grown in situ by molecular beam epitaxy and their electrical characteristics were measured. Effective barrier heights between 0.30 and 1.04 eV were determined through I‐V and C‐V measurements in the Al/Si/n‐GaAs structures under varying conditions of deposition of the silicon layer, in contrast to a barrier height of 0.78 eV without the silicon layer. The conduction‐band offset between Si and GaAs is estimated to be of the order of 0.3±0.05 eV. The results indicate that the Fermi level at the interface of GaAs on Si in the Al/Si/n‐GaAs structure is unpinned from its midgap value.

Class D current-driven rectifiers for resonant DC/DC converter applications

Abstract: Analyses and experimental results are given for a family of three Class D current-driven rectifiers. The diode current is half-sine wave and the diode voltage is a square wave. The diode forward voltage and forward resistance are taken into account in the analyses. The basic performance parameters of the rectifiers are determined, such as input resistance, voltage transfer function, efficiency, and power factor. The ripple voltage is estimated, and some effects of the equivalent series resistance and equivalent series inductance of filter capacitors on the ripples are discussed. The experimental results were obtained using IR31DQ06 Schottky diodes at 1 MHz and 16 W output power. >