Showing papers on "Depletion region published in 2000"

InP/InGaAs uni-travelling-carrier photodiode with 310 GHz bandwidth

Abstract: The authors have fabricated an InP-InGaAs uni-travelling-carrier photodiode that exhibits a 3 dB bandwidth of 310 GHz and a pulse width (FWHM) of 0.97ps. Both of which are record values for photodetectors operating at a wavelength of 1.55 /spl mu/m. The average electron velocity in the depletion region is estimated to be 3.0/spl times/10/sup 7/ cm/s.

Cellular trench-gate field-effect transistors

Abstract: A cellular trench-gate field-effect transistor comprises a field plate (38) on dielectric material (28) in a perimeter trench (18). The dielectric material (28) forms a thicker dielectric layer than the gate dielectric layer (21) in the array trenches (11). The field plate (38) is connected to the source (3) or trench-gate (31) of the transistor and acts inwardly towards the cellular array rather than outwardly towards the body perimeter (15) because of its presence on the inside wall (18a) of the trench (18) without acting on any outside wall (18b). The array and perimeter trenches (11, 18) are sufficiently closely spaced, and the intermediate areas (4a, 4b) of the drain drift region (4) are sufficiently lowly doped, that the depletion layer (40) formed in the drain drift region (4) in the blocking state of the transistor depletes the whole of these intermediate areas between neighbouring trenches at a voltage less than 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 cellular array.

Electronic properties of In2O3 surfaces

Abstract: Surfaces of reactively evaporated In2O3 films were investigated in situ by synchrotron-excited photoemission. Work function, valence band maximum, and electronic states in the band gap were determined as a function of oxygen pressure. Surface and bulk electronic properties can only be explained consistently with the assumption of a surface depletion layer.

Ionic Conductor Composites: Theory and Materials

Abstract: The main theoretical concepts on ionic conduction at interfaces, especially the space charge layer model, are summarized in the first part of this review: ion trapping or redistribution leads to charge carrier accumulation, depletion or inversion and, consequently, to conductivity changes in composite materials. Experimental confirmations of the space charge layer model and the complementary percolation model are discussed. Major developments of ionic conductor composite materials over the last 25 years are presented in the second part, including lithium and other alkaline ion conductors, copper and silver ion conductors, di- and trivalent cation and anion conductors, glass and polymer composites. Some future trends and research needs are indicated in conclusion.

Recombination mechanisms in amorphous silicon/crystalline silicon heterojunction solar cells

Abstract: This article investigates limitations to the open circuit voltage of n-type amorphous silicon/p-type crystalline silicon heterojunction solar cells. The analysis of quantum efficiency and temperature dependent current/voltage characteristics identifies the dominant recombination mechanism. Depending on the electronic quality of the crystalline silicon absorber, either recombination in the neutral bulk or recombination in the space charge region prevails; recombination at the heterointerface is not relevant. Although interface recombination does not limit the open circuit voltage, recombination of photogenerated charge carriers at the heterointerface or in the amorphous silicon emitter diminishes the short circuit current of the solar cells.

High breakdown voltage semiconductor device having trenched film connected to electrodes

Abstract: A plurality of trenches are formed in a drift region between a p-type body region and an-type buffer region. A silicon oxide film is formed on the side and bottom of each of the trenches, and an SIPOS film is buried into each of the trenches. The trenches are formed by RIE, and the SIPOS film is deposited by LPCVD and an undesired portion can be removed by dry etching such as RIE. The SIPOS film is connected to a source electrode at the source end of each trench, and it is connected to a drain electrode directly or through a resistor at the drain end thereof. When a high voltage is applied, a depletion layer expands in the n-type drift region from an interface between the n-type drift region and the trench on each side of the n-type drift region, therefore, the impurity concentration of the n-type drift region can be heightened without lowering the high breakdown voltage, and the resistance of the drift region can be decreased.

Phase modulator for semiconductor waveguide

Abstract: An optical phase modulator comprises a semiconductor rib wave guide having P and N doped regions forming a PN junction along the path of the rib with terminals for applying a reverse bias to the junction to extend a carrier depletion zone to alter the refractive index, the PN junction is offset from the central axis of the rib but on application of the reverse bias the depletion zone extends over a central axis of the waveguide.

High-quality p–n junctions with quaternary AlInGaN/InGaN quantum wells

Abstract: We report on quaternary AlInGaN/InGaN multiple quantum well (MQW) light emitting diode structures grown on sapphire substrates. The structures demonstrate high quality of the p–n junctions with quaternary MQW. At low forward bias (below 2 V), the temperature dependent of current–voltage characteristics are exponential with the ideality factor of 2.28, which is in a good agreement with the model of the injected carrier recombination in the space charge region. This ideality factor value is approximately three times lower than for conventional GaN/InGaN light emitting diodes (LEDs). The obtained data indicate the recombination in p–n junction space charge region to be responsible for a current transport in LED structures with quaternary quantum wells. This is in contrast to InGaN based LEDs, where carrier tunneling dominates either because of high doping of the active layer or due to the high density of localized states.

Depletion region effects in Mg-doped GaN

Abstract: The deep nature of the Mg acceptor will have important implications for the performance of high-speed GaN-based bipolar devices In this work, the effect of the deep acceptor on the band bending within the depletion region is examined in detail The width of the transition region, which separates the mobile holes from the space-charge edge, is carefully investigated High-frequency modulation of the depletion region is discussed for both the large- and small-signal cases For the small-signal case, calculated results are compared to experimental measurements of frequency-dependent capacitance which have been performed on Mg-doped GaN samples

Mosfet with field reducing trenches in body region

Abstract: A MOSFET device (100) that exhibits low power loss characteristics by minimizing source-to-drain channel on resistance includes a semiconductor block having at least two surfaces and a drift region (110) disposed within the semiconductor block; the drift region is characterized by a first conduction type and a first predetermined dopant concentration. A body region (104) with a second conduction type is disposed within the semiconductor block between and adjacent to the first surface and the drift region. A source region (142) is disposed within the semiconductor block, and is embedded in the body region so as to be adjacent to the body region and the first surface. The MOSFET device further includes at least one drain region disposed in the semiconductor block between the second surface and the drift region. An opening is formed in the body region, extending from the first surface and into the semiconductor block. The opening has one or more interior walls (106) that are doped with a dopant of the same conduction type as the body region, and at a second predetermined dopant concentration, so as to form a depletable region near the walls. A blocking voltage applied across the MOSFET device depletes charge carriers within the semiconductor block, so as to substantially prevent electrical current from flowing through the MOSFET between the source region and the drain region. The opening, or trench (102), in the device forces the depletion region to spread laterally within the drift region as blocking voltage increases.

A novel photodetector using MOS tunneling structures

Abstract: A metal/oxide/p-Si structure with ultrathin oxide is utilized as a photodetector. At positive gate bias, the dark current of the photodetector is limited by the thermal generation of minority carriers in the inversion layer. The high growth temperature (1000/spl deg/C) of the gate oxide can reduce the dark current to a level as low as 3 nA/cm/sup 2/. As biased in the inversion layer, the tunneling diode works in the deep depletion region with soft pinning of oxide voltage, instead of the pinning of surface potential, very different from the conventional MOS diode with thick oxide.

Effect of fill-pulse parameters on deep-level transient spectroscopy peaks in highly doped p-type InP

Abstract: The effect of different fill-pulse parameters on the characteristics of deep-level transient spectroscopy (DLTS) peaks has been studied in the example of the hole traps H4F and H5 in electron-irradiated highly doped p-type InP. It is shown that the saturation peak height, the temperature of the peak maximum and its full width at half maximum depend on the applied reverse bias, the pulse amplitude, its frequency and duration. Our results show that the origin of this dependence is the electric field present in the space charge region (SCR). The experimental results are analyzed in terms of the effect of the electric field on the refilled traps in the SCR. The appropriate experimental conditions for the correct extraction of information from the DLTS spectrum are defined.

Schottky effect model of electrical activity of metallic precipitates in silicon

Abstract: A quantitative model of the electrical activity of metallic precipitates in Si is formulated with an emphasis on the Schottky junction effects of the precipitate–Si system. Carrier diffusion and carrier drift in the Si space charge region are accounted for. Carrier recombination is attributed to the thermionic emission mechanism of charge transport across the Schottky junction rather than the surface recombination. It is shown that the precipitates can have a very large minority carrier capture cross-section. Under weak carrier generation conditions, the supply of minority carriers is found to be the limiting factor of the recombination process. The plausibility of the model is demonstrated by a comparison of calculated and available experimental results.

Sulfur passivation of GaAs metal-semiconductor field-effect transistor

Abstract: A passivation technique consisting of a (NH4)2S dip followed by GaS deposition has been applied to a GaAs microwave-power metal–semiconductor field-effect transistor (MESFET). The breakdown characteristic of the MESFET is greatly improved upon the (NH4)2S treatment, and a stable passivation effect can be achieved by GaS film deposition. It is found that the FET current–voltage characteristics are closely related to variations in the pinning position of the GaAs surface Fermi level. With the surface passivated, a depletion layer can be properly formed and protected, which is of benefit to the control of the device parameters.

Solid-state image-sensing device and method for producing the same

Abstract: A solid-state image-sensing device has pn-junction sensor parts isolated corresponding to pixels by a device isolation layer The solid-state image-sensing device includes a first-conductivity-type second semiconductor well region formed between a first-conductivity-type first semiconductor well region and the device isolation layer When the device is operating, a depletion layer of each sensor part spreads to the first semiconductor well region, which is beneath each of the sensor parts

Electronic transport in porous silicon of low porosity made on a p+ substrate

Abstract: To analyze the carriers transport in metal–porous silicon (PS) junctions, we studied the current–voltage and impedance characteristics of a series of junctions, having a typical porosity of 30% and a layer thickness ranging from 1.5 to 30 μm. PS conductivity as a function of the annealing temperature showed two characteristic regions at 150 and 550°C where the conductivity abruptly increased by several orders of magnitude. These temperatures coincide with the temperature of dissociation of Si–H–B complexes and of hydrogen effusion. After short time rinsing of high temperature annealed PS in hydrofluoric acid its resistivity returned to the initial high value it had in the as-prepared state. These results imply that hydrogen plays a key role in determining the conduction properties of PS. We argue that the hydrogen present in PS in high concentration effectively passivates the boron doping atoms. As a result the space charge region that compensates surface charges significantly widens and becomes essentially larger than the silicon wires which leads to the high resistivity of PS. Current–voltage dependencies exhibit a region of space charge limited current, which allows for the determination of the energy distribution density of states in PS.

Depletion region in thermally poled fused silica

Abstract: The depletion-layer width and the recorded electric field in thermally poled fused silica are investigated experimentally as a function of the applied voltage. The depletion-layer width is observed to vary linearly with the poling voltage. The average electric field recorded in the depletion region was found to be (5.3±0.3)×108 V/m for all samples, independently of the poling voltage.

DEPLETION-REGION RECOMBINATION IN SILICON SOLAR CELLS: WHEN DOES mDR

Abstract: This paper examines the ideality factor of depletion-region recombination mDR, with a particular emphasis on its maximum value. Several theoretical models of depletion-region recombination are discussed and it is shown that the models with more assumptions tend to overestimate mDR. Numerical simulations are then used to determine the maximum value of mDR for both step-junction and di usedjunction solar cells, for the case when the trap density is uniformly distributed across the depletion region. The maximum value of mDR is found to increase with doping from 1.7 to 2 for step junctions; and to be approximately 1.8 for all practical doping levels of di used junctions.

Current transport mechanism of p-GaN Schottky contacts

Abstract: Transient measurements of I–V and depletion layer capacitance were conducted to clarify the leaky current flow mechanism in Ni Schottky contacts formed on Mg-doped p-GaN. We found that carrier capture and emission from acceptor-like deep level defects cause depletion layer width (Wdep) to vary significantly. Upon ionization of the defects by white light, which results in small Wdep, current can go through the Schottky barrier and a leaky I–V curve is observed. Upon filling by current injection, Wdep becomes larger and the large original Schottky barrier height is seen. The time constant of carrier emission is as long as 8.3×103 min.

Undoped-emitter InP/InGaAs HBTs for high-speed and low-power applications

Abstract: Scaling down the lateral emitter dimension is an effective way to reduce the power dissipation of HBT ICs. Various authors have demonstrated submicrometer HBTs operating at >100 GHz with submilliampere current. On the other hand, there have been few reports on vertical layer structures optimized for low-current operation. At low current, the dominant delay time of HBTs is the emitter charging time. Thus, it is essential to reduce the emitter junction capacitance by increasing the thickness of the emitter depletion layer. In this paper, we propose an undoped-emitter structure for InP-based HBTs and investigate its impact on low-power applications.

Photoelectrochemical Characteristics Of α-Fe2O3 Nanocrystalline Semiconductor Thin Film

Abstract: α-Fe2O3 single crystal thin films have been prepared from 45 nm diameter colloid. These thin nanocrystalline films exhibit a typical behavior of n-type semiconductor material because of the anodic photocurrent generation. The anodic photocurrent response upon illumination and the reversal spike of cathodic current upon the light switched off suggests that the electrons can flow in both directions and no space charge layer exists at the thin film/electrolyte interface. The decreased photocurrent responses of thicker films can be explained by the electric resistance effect and recombination effect. Moreover, the thicker film will lead to a poor photocurrent response for short wavelength light. Considering the use of sunlight, the thin film thickness should be controlled to an optimal value.

Hydrodynamic-flow-driven wetting in thin film polymer blends: growth kinetics and morphology

Abstract: A thin film of deuterated poly(methyl methacrylate) (A) and poly(styrene-ran-acrylonitrile) at the critical composition is annealed in the two phase region to induce simultaneous phase separation and wetting of the A-rich phase at the surface. Using forward recoil spectrometry, the wetting layer thickness is found to grow linearly with time at $185\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and $190\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ After selective etching of A, atomic force microscopy reveals a depletion layer having a bicontinuous, phase separated morphology. The A-rich tubes in this layer provide a pathway for rapid transport of the wetting phase from the bulk to the surface via hydrodynamic flow. Taken together, fast wetting layer growth ${t}^{1}$ and connectivity between the wetting layer and bulk provide unambiguous support for hydrodynamic-flow-driven wetting in thin film polymer blends.

Implications of radiation-induced dopant deactivation for npn bipolar junction transistors

Abstract: Metal-oxide-silicon capacitors fabricated in a bipolar process were examined for densities of oxide trapped charge, interface traps and deactivated substrate acceptors following high-dose-rate irradiation at 100/spl deg/C. Acceptor neutralization near the Si surface occurs most efficiently for small irradiation biases in depletion. The bias dependence is consistent with compensation and passivation mechanisms involving the drift of H/sup +/ ions in the oxide and Si layers and the availability of holes in the Si depletion region. The capacitor data were used to simulate the impact of acceptor neutralization on the current gain of an irradiated npn bipolar transistor. Neutralized accepters near the base surface enhance current gain degradation associated with radiation-induced oxide trapped charge and interface traps by increasing base recombination. The additional recombination results from the convergence of carrier concentrations in the base and increased sensitivity of the base to oxide trapped charge. The enhanced gain degradation is moderated by increased electron injection from the emitter. These results suggest that acceptor neutralization may complicate hardness assurance test methods for linear circuits, which are based on elevated temperature irradiations.

Fabrication of a field effect transistor with minimized parasitic Miller capacitance

Abstract: A field effect transistor is fabricated to have a drain overlap and a source overlap to minimize series resistance between the gate and the drain and between the gate and the source of the field effect transistor. The parasitic Miller capacitance formed by the drain overlap and the source overlap is reduced by forming a depletion region at the sidewalls of the gate structure of the field effect transistor. The depletion region at the sidewalls of the gate structure is formed by counter-doping the sidewalls of the gate structure. The sidewalls of the gate structure at the drain side and the source side of the field effect transistor are doped with a type of dopant that is opposite to the type of dopant within the gate structure. Such dopant at the sidewalls of the gate structure forms a respective depletion region from the sidewall into approximately the edge of the drain overlap and source overlap that extends under the gate structure to reduce the parasitic Miller capacitance formed by the drain overlap and the source overlap.