Schottky Barrier Characteristics Research Articles

Investigations of ammonium sulfide surface treatments on GaAs

X-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED) results are presented for ammonium sulfide treated (100)GaAs surfaces. XPS shows that the sulfur coverage is independent of the ammonium sulfide concentration, although the relative amount of arsenic decreases as the sulfide concentration increases. RHEED patterns show that higher temperatures are required for the surface to restructure following treatment with higher sulfide concentration. In addition to the order of magnitude changes in the diode saturation current densities following ammonium sulfide treatment, we observe that the characteristics of gold and aluminum Schottky barriers on sulfide-treated GaAs surfaces also vary with the substrate temperature during metal deposition.

Schottky barrier height variation due to a Mo interfacial layer in W/GaAs systems

The effect of the interfacial Mo-GaAs alloy layer on the Schottky barrier characteristics of W/GaAs contacts is investigated. Variation in Schottky barrier heights is measured by fabricating W(300 nm thick)/Mo(0–10 nm)/GaAs diodes, where a Ga2 O3 layer 0.9 nm thick is previously formed on the GaAs surface. The oxide layer is intended to detect the initial stage of the interfacial reaction which could remove the oxide layer and influence electrical characteristics. The maximum barrier height and the minimum ideality factor are obtained at a Mo layer thickness of 1 nm after annealing at 450 °C. The Mo layer reduces the Ga2 O3 layer on GaAs surfaces and forms the compounds GaMo3 and Mo5 As4 with the GaAs substrates by a solid-phase reaction. The intimate contact of these compounds to the substrates is thought to be formed some distance below the original Mo/GaAs interface. The formation and control of buried Schottky barrier contacts using refractory metals are experimentally verified. This allows more reliable gate barriers for GaAs metal-semiconductor field-effect transistors.

Conductivity Modulation Effect in High Voltage N-Channel Schottky Injection FETs

In this paper, the conductivity modulation effect in high voltage (570V) n-channel Schottky Injection FET (SINFET) is analyzed. The conductivity modulation effect, which is dependent on the Schottky barrier characteristics and the device structure, is evaluated in terms of the onset voltage for conductivity modulation. Results show that the onset voltage for conductivity modulation of the drift region increases with increasing drift region length and Schottky contact width, but decreases with increasing drift region dose. Finally, a comparison of the DC and switching performance of the LDMOST, various types of LIGBTs, and SINFET devices is given.

Influence of the Defect Density of Amorphous Silicon at the Substrate Interface on the Schottky Barrier Characteristics

Influence of the Defect Density of Amorphous Silicon at the Substrate Interface on the Schottky Barrier Characteristics

Effect of the defectiveness of a semiconductor on the characteristics of Pd-GaAs contacts

A study was made of the volt-ampere characteristics of Pd-GaAs Schottky barriers in relation to the defectiveness of the gallium arsenide. The defect content of the material was checked metallographically and by the method of x-ray topography. Single crystals of GaAs doped with Ge, Ge + Sb, and Ge + In were studied. Here, the electron concentration was (1–4) · 1015 cm−3, and mean dislocation density ranged from 4·104 to 2·102 cm−2. The defectiveness of the material was altered by the introduction of different concentrations of isovalent impurities. It was shown that for diodes produced by the same technology, the manifestation of low-temperature VAC anomalies and the current mechanism are determined by structural features of the semiconductor (by dislocations and microdefects).

Electrical characteristics of diodes fabricated in selective-epitaxial silicon wells

The selective epitaxial growth of silicon using SiO 2 as a mask is investigated in this work. The silicon films were deposited using SiCl 4, H 2 and HCl in an atmospheric reactor at 1050°C. The structural aspects and electrical characteristics of Schottky barrier and diffused PN diodes fabricated in silicon islands formed with the selective-epitaxial deposition technique are reported. The influence of substrate resistivity and reactive ion teching on the quality of the selective-epi is examined and found to have no effect on the electrical characteristics. Diodes fabricated inside selective-epitaxial silicon wells far from the edges of the wells have different characteristics than those that include the edges and these differences are discussed.

A Study of the State Distribution in Various a-Si:H Materials by a New Capacitance Method

AbstractA new method for the determination of the deep states density in amorphous semiconductors is presented. The method is based on the carriersemission- time dependence of the capacitance-voltage characteristics of Schottky barriers. The applicability of the method for the study of hydrogenated amorphous silicon materials is demonstrated. The pitfalls associated with trying to deduce the density of states from a single capacitance-voltage characteristic are also discussed.

Growth of In0.53Ga0.47As by liquid phase epitaxy over tungsten on structured InP substrates

A first study involving lateral growth of In0.53Ga0.47As by liquid phase epitaxy over tungsten metal is being reported. Because of the rapid lateral nucleation process in the channels etched on (111) B InP substrates, seeding of the crystal through the metal layer is found unnecessary, enabling growth to occur over relatively large areas of continuous metal. The tungsten metal during growth was found to remain undissolved in the growth solution, and also acted as a mask for vertical growth when used on a plane InP substrate. The Schottky barrier characteristics between the tungsten and the top InGaAs layer indicate that this structure will be useful for metal base transistors.

Comparison of low temperature and high temperature refractory metal/silicides self-aligned gate on GaAs

Since the first reported use of TiW gate as a stopping mask for n+ implantation for GaAs self-aligned gate field effect transistors (SAGFET) in 1981, refractory metal compounds and silicides have found a widespread use in the GaAs SAGFET technology. However, the technique requires that the refractory metal (silicide)/GaAs interface be subjected to a high temperature postimplantation annealing, typically 750–900 °C. The mechanical, metallurgical, and most sensitively the electrical stabilities and reproducibility of the refractory metal (silicide)/GaAs Schottky barrier characteristics have become the major issues confronting the high temperature SAGFET technology. The use of a dielectric substitutional gate, which allows the refractory metal gate to be formed at a low temperature, typically room temperature to 400 °C, for fabrication of SAGFET was reported in 1983. With the advance of well controlled dry etching and photoresist planarization techniques, the low temperature SAGFET process becomes a potentially viable alternate technology. In this paper, comparisons of the two technologies and associated device performances are made. The basic issues of refractory metal/GaAs and dielectric/GaAs interface reactions, stress and impurity incorporation at high annealing temperatures are discussed.

The effect of carrier concentration in the semiconductor on the voltage-current characteristics of Schottky barrier diodes at low temperatures

We report the results of a study of voltage-current characteristics of gallium arsenide metal-semiconductor Schottky barrier structures, in which palladium and W-Ni alloy were electrochemically deposited in SiO2 windows to form the barrier. It is demonstrated that the voltage-current characteristics are significantly distorted at low temperatures. The observed behavior of the voltage-current characteristics at low temperatures —the appearance of excess current and the increase in the ideality factor with carrier concentration in the excess current regime —is explained by a model in which peripheral mechanical stresses in the contacts lower the potential barrier height on the periphery of the contacts.

Effect of impurity trapping on the capacitance-voltage characteristics of n-GaAs/N-AlGaAs heterojunctions

We have studied the capacitance-voltage (C-V) characteristics of Schottky barriers on inverted n-GaAs/N-AlGaAs and normal N-AlGaAs/n-GaAs heterojunctions. Impurities introduced during film growth produced a negative sheet charge of 6.0×1011 cm−2 at the interface of the inverted n-GaAs/N-AlGaAs heterojunction. The effectiveness of GaAs quantum wells in trapping these impurities was investigated. GaAs quantum wells 20 Å wide were placed in intervals of 2500 Å for the first 0.75 μm of the AlGaAs layer; in the last 0.25 μm, the periodicity of the quantum wells was progressively decreased by half with the last quantum well placed at about 160 Å from the GaAs/AlGaAs interface. The resulting measured interface charge concentration of 4.4×1010 cm−2 is more than a magnitude lower than measured before the use of the quantum wells and is essentially at the limit of the accuracy of the C-V technique for this structure.

Optical beam characteristics of Schottky barrier confined arrays of phase-coupled multiquantum well GaAs lasers

The characteristics of phase-coupled laser arrays fabricated using Schottky barriers on the p-contact to confine the current flow to 5 or 10 stripes on 9 μm centers are described. The gain guided laser spots are very equally spaced, and in some cases do not coincide exactly with the position or number of conducting stripes. The self adjusting nature of the active region, together with the phase shift of π between the neighboring <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> laser spots results in extremely smooth far-field patterns consisting of 2 narrow, intense outer lobes, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N-2</tex> much weaker interior lobes. The mode structure closely approximates the higher order modes observed in wide stripe laser. The separation and width of the outer lobes is defined by diffraction theory, and determined by the separation and number of lasing spots. Deviations from diffraction theory are found in some cases. The contributions to the far field were studied by examining the magnified image of the exit facet as a narrow slit was passed across the far field. The phase contributions present in the far field were studied by introducing a relative phase shift between the two symmetric halves of the far field. The relative phase change modifies the interference pattern of the magnified near-field image, causing a spatial shift of the imaged spots in the plane of the junction.

Two-step Al/Ti metallization to PtSi/Si structures

A two-step Al metallization procedure to prevent Al degradation of PtSi/Si Schottky barrier characteristics has been evaluated using Al3Ti as the kinetic barrier to the consumption of Ti. In the first step a thin Al layer is deposited on a Ti layer on PtSi/Si and is heated to the standard metallization process temperature of 450–500 °C. The Al and Ti thicknesses are chosen so that the Al is consumed to form Al3Ti with Ti remaining between the aluminide and silicide. In the second step a thick layer of Al, compatible with interconnect requirements, is deposited and annealed at temperatures around 350 °C. The formation rate of Al3Ti at this temperature is sufficiently low that consumption of Ti is minimal and the electrical characteristic of the PtSi/Si contact is preserved.

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Amorphous metal-semiconductor contacts for high temperature electronics—II Thermal stability of Schottky barrier characteristics

We report results on the thermal stability of the Schottky barrier formed by each of two amorphous metal alloys (from the NiNb and TaIr systems) on Si and GaAs. We have found the barrier height to be stable to within 0.05 eV after treatment for 2.5 hr at 500°C in the case of TaIr/ n/ n + GaAs, and within 0.06 eV after treatment for 40 hr at 350°C in the case of TaIr/ n/ n + Si.

Amorphous metal-semiconductor contacts for high temperature electronics—I Materials and characterisation

In this and a companion paper, we summarise the achievement of a metal-semiconductor contact whose electrical characteristics degrade only over tens of hours at 500°C. Although initially conceived as a barrier to Au diffusion, the thin amorphous metal film now fails because of out-diffusion of elements of the semiconductor. In this paper we summarise the rationale for using amorphous metal films, the choice of alloys, the fabrication of test structures, and the characterisation of these structures before and after exposure to temperatures as high as 700°C for 24 hr. The companion paper describes the thermal degradation of Schottky barrier characteristics of metal films on both Si and GaAs.

Semitransparent Silicide Electrode Formed on the Surface of a-Si:H

ABSTRACTThin silicide layers are found to be formed through solid state reaction between hydrogenated amorphous silicon(a-Si:H) and metals. The method of formation of the silicide layer is very simple: deposition of metal on top of amorphous silicon layer and annealing and etching of the residual metal layer. The reaction kinetics and properties of this layer are described. The thickness of this silicide layer is estimated to be 5 nm. Accordingly, it can be used as a transparent electrode in a-Si:H photodiodes. Photodiodes using this semitransparent electrode have as good optical and electrical properties as conventional a-Si:H photodiodes using ITO(indium tin oxide). Schottky barrier characteristics are also de-scribed.

EFFECT OF HEATING SAMPLES DURING PULSED ELECTRON BEAM ANNEALING ON THE OPEN-CIRCUIT VOLTAGE OF SILICON SOLAR CELLS

500 mV). Their nature is discussed on the basic of S.E.M. observations, D.L.T.S. study and degradation of electrical characteristics of Schottky barriers. An improved PEBA process is determined, characterized by a low mean energy electron beam (10 keV) associated to a starting temperature of 450°C and low fluences

The effect of substrate-epitaxial interface on the capacitance-voltage characteristics of Schottky barriers formed on sputtered films of gallium arsenide: A K Kalkurni and R J Soukup, J Vac Sci Technol, 20 (3), 1982, 807–810

The effect of substrate-epitaxial interface on the capacitance-voltage characteristics of Schottky barriers formed on sputtered films of gallium arsenide: A K Kalkurni and R J Soukup, J Vac Sci Technol, 20 (3), 1982, 807–810

The effect of substrate–epitaxial interface on the capacitance–voltage characteristics of Schottky barriers formed on sputtered films of gallium arsenide

The capacitance–voltage characteristics of Schottky diodes fabricated on sputtered GaAs do not yield straight line plots on a 1/C2 vs V curve. This anomalous behavior may be due to any one of the following mechanisms: (1) defective Schottky barrier fabrication, (2) the effect of an insulating interfacial layer, (3) nonuniform donor distribution, (4) the effect of deep traps, or (5) the effect of the substrate–epitaxial interface. Only the effect of the substrate–epitaxial interface capacitance adequately explains the anomalous behavior observed. Measurements of capacitance at 1 kHz and at 1 MHz coupled with complex impedance measurements led to a small signal linear circuit model. The temperature dependence of the circuit elements identified appropriately with physical phenomena yielded information about the Schottky barrier and the barrier formed at the epitaxial layer–substrate interface. The strong temperature dependence of the low–high junction barrier capacitance is explained using this model.