Showing papers on "Depletion region published in 2008"

XBn Barrier Photodetectors for High Sensitivity and High Operating Temperature Infrared Sensors

Abstract: A barrier photodetector is a device in which the light is absorbed in a narrow bandgap semiconductor layer whose bands remain essentially flat or accumulated at the operating bias so that all carrier depletion is excluded. In a conventional photodiode below a threshold temperature T0, typically 130-150K for MWIR devices, the dark current is due to Generation-Recombination (G-R) centres in the depletion layer. In a barrier detector, the absence of depletion in the narrow bandgap semiconductor ensures that the G-R contribution to the dark current is negligible. The dark current in the barrier detector is thus dominated by the diffusion component, both above and below T0. Therefore, at a given temperature below T0, a barrier detector will exhibit a lower dark current than a conventional photodiode with the same cut-off wavelength. Alternatively, for a given dark current, a barrier detector will operate at a higher temperature than a conventional photodiode, provided that this temperature is below T0. Device architectures are presented for barrier detectors with photon absorbing layers based on InAs1-xSbx alloys and type-II InAs/GaSb superlattices (T2SL). The thermionic and tunneling components of the dark current are analyzed and shown to be negligible for typical device parameters. An operating temperature of ~150K is estimated for a MWIR barrier detector with f/3 optics and a cut-off wavelength of 4.2μ.

Efficient Schottky-quantum-dot photovoltaics: The roles of depletion, drift, and diffusion

Abstract: PbS colloidal quantum dot photovoltaic devices in a Schottky architecture have demonstrated an infrared power conversion efficiency of 4.2%. Here, we elucidate the internal mechanisms leading to this efficiency. At relevant intensities, the drift length is 10μm for holes and 1μm for electrons. Transport within the 150nm wide depletion region is therefore highly efficient. The electron diffusion length of 0.1μm is comparable to neutral region width. We quantitatively account for the observed 37% external quantum efficiency, showing that it results from the large depletion width and long carrier lifetime combined.

Reducing high-frequency signal loss in substrates

Abstract: An integrated circuit structure includes a semiconductor substrate of a first conductivity type; and a depletion region in the semiconductor substrate. A deep well region is substantially enclosed by the depletion region, wherein the deep well region is of a second conductivity type opposite the first conductivity type. The depletion region includes a first portion directly over the deep well region and a second portion directly under the deep well region. An integrated circuit device is directly over the depletion region.

Electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays

Abstract: We describe the electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays fabricated on doped semiconductor substrates. The hybrid metal-semiconductor forms a Schottky diode structure, where the active depletion region modifies the substrate conductivity in real-time by applying an external voltage bias. This enables effective control of the resonance enhanced terahertz transmission. Our proof of principle device achieves an intensity modulation depth of 52% by changing the voltage bias between 0 and 16 volts. Further optimization may result in improvement of device performance and practical applications. This approach can be also translated to the other optical frequency ranges.

Electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays

Abstract: We describe the electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays fabricated on doped semiconductor substrates. The hybrid metal-semiconductor forms a Schottky diode structure, where the active depletion region modifies the substrate conductivity in real-time by applying an external voltage bias. This enables effective control of the resonance enhanced terahertz transmission. Our proof of principle device achieves an intensity modulation depth of 52% by changing the voltage bias between 0 and 16 volts. Further optimization may result in improvement of device performance and practical applications. This approach can be also translated to the other optical frequency ranges.

Field-Effect Semiconductor Device, and Method of Fabrication

Abstract: A HEMT-type field-effect semiconductor device has a main semiconductor region comprising two layers of dissimilar materials such that a two-dimensional electron gas layer is generated along the heterojunction between the two layers. A source and a drain electrode are placed in spaced positions on a major surface of the main semiconductor region. Between these electrodes, a gate electrode is received in a recess in the major surface of the main semiconductor region via a p-type metal oxide semiconductor film whereby a depletion zone is normally created in the electron gas layer, with a minimum of turn-on resistance and gate leak current.

Background limited long wavelength infrared type-II InAs/GaSb superlattice photodiodes operating at 110 K

Abstract: The utilization of the P+-π-M-N+ photodiode architecture in conjunction with a thick active region can significantly improve long wavelength infrared type-II InAs/GaSb superlattice photodiodes. By studying the effect of the depletion region placement on the quantum efficiency in a thick structure, we achieved a topside illuminated quantum efficiency of 50% for an N-on-P diode at 8.0 μm at 77 K. Both the double heterostructure design and the application of polyimide passivation greatly reduce the surface leakage, giving an R0A of 416 Ω cm2 for a 1% cutoff wavelength of 10.52 μm, a Shot–Johnson detectivity of 8.1×1011 cmHz/W at 77 K, and a background limited operating temperature of 110 K with 300 K background.

Light emitting devices having current reducing structures and methods of forming light emitting devices having current reducing structures

Abstract: A light emitting device includes a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer. A non-transparent feature, such as a wire bond pad, is on the p-type semiconductor layer or on the n-type semiconductor layer opposite the p-type semiconductor layer, and a reduced conductivity region is in the p-type semiconductor layer or the n-type semiconductor layer and is aligned with the non-transparent feature. The reduced conductivity region may extend from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region and/or from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region.

The role of image charges in the interactions between colloidal particles

Abstract: The dielectric interiors of colloidal particles are responsible for dispersion (van der Waals) interactions. However, these dielectric regions also alter the manner in which charges, such as on ions or other colloidal particles, interact with each other, due to the induction of charges at the dielectric interfaces. The impact of these induced charges can be represented in terms of “image charges”. These image charges result in an ion depletion layer in the vicinity of low dielectric bodies. This depletion layer is responsible for the increase in the surface tension of water upon the addition of electrolytes. In the case of colloidal particles, this depletion layer also leads to an “electrostatic depletion force” with a range of the order of a Bjerrum length. The relevance of this force to the salting out of proteins is discussed. This electrostatic depletion force is directly analogous to the entropically driven depletion force (due to excluded volume). Although image charge effects have been known, their influence on the behavior of colloidal systems, especially in the presence of mobile ions, has generally not been accounted for (e.g., DLVO theory). We review the previous theoretical and simulation studies of how image charges influence the properties of electrolyte and colloidal systems and discuss the relevance of these effects on experimental systems.

New High-Voltage ( $>$ 1200 V) MOSFET With the Charge Trenches on Partial SOI

Abstract: A novel silicon-on-insulator (SOI) high-voltage MOSFET structure and its breakdown mechanism are presented in this paper The structure is characterized by oxide trenches on the top interface of the buried oxide layer on partial SOI (TPSOI) Inversion charges located in the trenches enhance the electric field of the buried layer in the high-voltage blocking state, and a silicon window makes the depletion region spread into the substrate Both of them modulate the electric field in the drift region; therefore, the breakdown voltage (BV) for a TPSOI LDMOS is greatly enhanced Moreover, the Si window alleviates the self-heating effect The influences of the structure parameters on device characteristics are analyzed for the proposed device structure The TPSOI LDMOS with BV > 1200 V and the buried-layer electric field of EI > 700 V/ mum is obtained by the simulation on a 2-mum-thick SOI layer over 2-mum-thick buried oxide layer, and its maximal temperature reduces by 19 and 87 K in comparison with the conventional SOI and partial SOI devices

Leakage current mechanisms in top-gate nanocrystalline silicon thin film transistors

Abstract: The leakage current in the top-gate nanocrystalline silicon (nc-Si:H) thin film transistors was examined at various temperatures in an attempt to deduce the underlying off-state conduction mechanisms. Under high gate bias, the leakage current can be attributed to the thermal emission of trapped carriers at the midgap grain boundary states at low drain bias, while the behavior is reminiscent of the Poole–Frenkel emission in the drain depletion region at high drain bias. In contrast, Ohmic conduction through the bulk nc-Si:H channel layer seems to be the dominant mechanism of the leakage current under low gate bias.

Photocurrent enhancement of SnO2 nanowires through Au-nanoparticles decoration.

Abstract: It is found that the sensitivity of photoresponse of SnO2 nanowires can be enhanced by metallic particles decoration. The underlying mechanism is attributed to the formation of the Schottky junction on nanowires surface in the vicinity of metallic nanoparticles. The increment in the barrier height and width of space charge region due to the existence of Schottky junction increases the surface electric field and enhances the spatial separation effect, which then prolongs the lifetime of photoinduced electron and consequently increases the photoresponse gain. The result shown here provides an alternative route for enhancing the photoresponse of semiconductor nanostructures, which should be useful for creating highly sensitive photodetectors.

Silicon carbide semiconductor device and related manufacturing method

Abstract: An SiC semiconductor device and a related manufacturing method are disclosed having a structure provided with a p + -type deep layer formed in a depth equal to or greater than that of a trench to cause a depletion layer between at a PN junction between the p + -type deep layer and an n − -type drift layer to extend into the n − -type drift layer in a remarkable length, making it difficult for a high voltage, resulting from an adverse affect arising from a drain voltage, to enter a gate oxide film. This results in a capability of minimizing an electric field concentration in the gate oxide film, i.e., an electric field concentration occurring at the gate oxide film at a bottom wall of the trench.

Dissipative particle dynamics simulation of depletion layer and polymer migration in micro- and nanochannels for dilute polymer solutions.

Abstract: The flows of dilute polymer solutions in micro- and nanoscale channels are of both fundamental and practical importance in variety of applications in which the channel gap is of the same order as the size of the suspended particles or macromolecules. In such systems depletion layers are observed near solid-fluid interfaces, even in equilibrium, and the imposition of flow results in further cross-stream migration of the particles. In this work we employ dissipative particle dynamics to study depletion and migration in dilute polymer solutions in channels several times larger than the radius of gyration (Rg) of bead-spring chains. We compare depletion layers for different chain models and levels of chain representation, solvent quality, and relative wall-solvent-polymer interactions. By suitable scaling the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. In Poiseuille flow, polymer migration across the streamlines increases with the Peclet and the Reynolds number until the center-of-mass distribution develops two symmetric off-center peaks which identify the preferred chain positions across the channel. These appear to be governed by the balance of wall-chain repulsive interactions and an off-center driving force of the type known as the Segre-Silberberg effect.

Semiconductor device and method of manufacturing the same

Abstract: A bipolar type semiconductor device capable of attaining high current gain and high cut-off frequency and performing a satisfactory transistor operation also in a high current region while maintaining a high breakdown voltage performance, as well as a method of manufacturing the semiconductor device, are provided. In a collector comprising a first semiconductor layer and a second semiconductor layer narrower in band gap than the first semiconductor layer, an impurity is doped so as to have a peak of impurity concentration within the second collector layer and so that the value of the peak is higher than the impurity concentration at any position within the first collector layer. It is preferable to adjust the concentration of the doped impurity in such a manner that a collector-base depletion layer extends up to the first collector layer.

Formation of ionic depletion/enrichment zones in a hybrid micro-/nano-channel

Abstract: This study fabricates a cross-form microchip in which the two side channels are attached to the main channel via a nanochannel bridge Ionic depletion and enrichment zones are established on the anodic and cathodic sides of the nanochannel Results show that the low conductivity within the depletion zone induces a rapid electroosmotic flow, which in turn prompts the generation of vortex flow structures within the depletion zone Both the lengthening of the depletion bulk charge layer and decrease in length of the diffusion layer as the applied voltage is increased are also demonstrated in this study

Quantum Detection Efficiency in Geiger Mode Avalanche Photodiodes

Abstract: The fabrication of silicon shallow junction photodiodes is a relevant topic for the detection of blue and near ultraviolet weak photon fluxes. In this paper we present a simple model to calculate the quantum detection efficiency (QDE) of a Geiger mode avalanche photodiode (GMAP) as a function of the dead layer thickness above the junction depletion layer. A comparison between calculated and experimental data is also presented. Moreover, by using the same model, an analysis of the QDE at 420 nm wavelength of conventional GMAPs based on shallow N+-P and P+-N junctions is given.

Laser-Induced Current Transients in Silicon-Germanium HBTs

Abstract: Device-level current transients are induced by injecting carriers using two-photon absorption from a subbandgap pulsed laser and recorded using wideband transmission and measurement equipment. These transients exhibit three distinct temporal trends that depend on laser pulse energy as well as the transverse and vertical charge generation location. The nature of the current transient is controlled by both the behavior of the subcollector-substrate junction and isolation biasing. However, substrate potential modulation, due to deformation of the subcollector-substrate depletion region, is the dominant mechanism affecting transient characteristics.

Single-photon avalanche photodiodes with integrated quenching resistor

Abstract: In this paper we present the results of the first electrical and optical characterization performed on STMicroelectronics new photosensor technology based on silicon single-photon avalanche photodiodes (SPAD). On the prospective of the design and the manufacturing of large-area silicon photomultipliers to be used as photodetectors for nuclear medicine imaging applications, we have modified our previous SPAD technology by means of the integration of a high-value quenching resistor to the photodiode. Moreover, an appropriate antireflective coating layer and the reduction of the quasi-neutral region thickness above the thin junction depletion layer have been introduced in the process flow of the device to enhance its spectral response in blue and near ultraviolet wavelength ranges. High gain, low leakage currents, low dark noise, very good quantum detection efficiency in blue–near UV ranges and a good linearity of the photodiode response to the incident luminous flux are the main characterization results.

Electrical characterization of CeO2∕Si interface properties of metal-oxide-semiconductor field-effect transistors with CeO2 gate dielectric

Abstract: Metal-oxide-semiconductor field-effect transistors with CeO2 gate dielectrics were fabricated. The lowest interface trap density (Dit) of CeO2∕Si interface in comparison with other high-κ gated diodes is 1.47×1012cm−2eV−1 due to the very low lattice mismatch of CeO2∕Si. The interfacial properties were characterized by gated-diode measurements. The surface recombination velocity (s0) and the minority carrier lifetime in the field-induced depletion region (τ0,FIJ) measured from the gated diodes are about 1.03×104cm∕s and 2.73×10−8s, respectively. The effective capture cross section of surface state (σs) extracted using the gated diode technique and the subthreshold swing measurement is about 8.68×10−15cm2.

DNA-modified indium phosphide Schottky device

Abstract: High quality Schottky sandwich devices were fabricated on an InP single crystal by solution processing a semiconducting polymer, DNA, as the metal electrodes We observed that DNA-based on this structure showed an excellent rectifying behavior with a typical ideality factor of 126, and that DNA film increased the effective barrier height by influencing the space charge region of InP Modeling, which includes a transport mechanism, reveals thermionic emission to be the dominant transport mechanisms for the diode (ideality factor n<13) We proposed that DNA could be a semiconductorlike material with a wide optical band energy gap of 395eV from its optical absorbance characteristics We also evaluated photovoltaic characteristic of the device under an illumination condition

Electrical characterization of organic-on-inorganic semiconductor Schottky structures

Abstract: We prepared a methyl red/p-InP organic–inorganic (OI) Schottky device formed by evaporation of an organic compound solution directly to a p-InP semiconductor wafer. The value of the optical band gap energy of the methyl red organic film on a glass substrate was obtained as 2.0 eV. It was seen that the Al/methyl red/p-InP contacts showed a good rectifying behavior. An ideality factor of 2.02 and a barrier height (Φb) of 1.11 eV for the Al/methyl red/p-InP contact were determined from the forward bias I–V characteristics. It was seen that the value of 1.11 eV obtained for Φb for the Al/methyl red/p-InP contact was significantly larger than the value of 0.83 eV for conventional Al/p-InP Schottky diodes. Modification of the interfacial potential barrier for the Al/p-InP diode was achieved using a thin interlayer of the methyl red organic semiconductor. This ascribed to the fact that the methyl red interlayer increases the effective Φb by influencing the space charge region of InP.

Mechanism of dislocation-governed charge transport in schottky diodes based on gallium nitride

Abstract: A mechanism of charge transport in Au-TiB x -n-GaN Schottky diodes with a space charge region considerably exceeding the de Broglie wavelength in GaN is studied. Analysis of temperature dependences of current-voltage (I–V) characteristics of forward-biased Schottky barriers showed that, in the temperature range 80–380 K, the charge transport is performed by tunneling along dislocations intersecting the space charge region. Estimation of dislocation density ρ by the I–V characteristics, in accordance with a model of tunneling along the dislocation line, gives the value ρ ≈ 1.7 × 107 cm−2, which is close in magnitude to the dislocation density measured by X-ray diffractometry.

Silicon depletion layer actuators

Abstract: The uncompensated donor or acceptor atoms present within the depletion layer of a diode can be employed in an electrostatic actuator, which utilizes the force between opposing charges on either side of the semiconductor junction. We describe the theory of this actuator and demonstrate its application for the case of a diode on the top surface of a silicon cantilever. The Schottky diodes fabricated on the top surface of cantilevers were used to drive them into resonance. As the actuator driving voltages are varied, the amplitude of vibration of the cantilevers changes, which is in agreement with the theoretical predictions.