Showing papers on "Diode published in 2007"

40 Gbit/s silicon optical modulator for highspeed applications

Abstract: A high-speed silicon optical modulator based on the free carrier plasma dispersion effect is presented. It is based on carrier depletion of a pn diode embedded inside a silicon-on-insulator waveguide. To achieve high-speed performance, a travelling-wave design is used to allow co-propagation of the electrical and optical signals along the length of the device. The resulting modulator has a 3 dB bandwidth of ~30 GHz and can transmit data up to 40 Gbit/s.

Compact, thermal-noise-limited optical cavity for diode laser stabilization at 1×10 −15

Abstract: We demonstrate phase and frequency stabilization of a diode laser at the thermal noise limit of a passive optical cavity. The system is compact and exploits a cavity design that reduces vibration sensitivity. The subhertz laser is characterized by comparison with a second independent system with similar fractional frequency stability (1x10(-15) at 1 s). The laser is further characterized by resolving a 2 Hz wide, ultranarrow optical clock transition in ultracold strontium.

Remotely powered self-propelling particles and micropumps based on miniature diodes.

Abstract: Microsensors and micromachines that are capable of self-propulsion through fluids could revolutionize many aspects of technology. Few principles to propel such devices and supply them with energy are known. Here, we show that various types of miniature semiconductor diodes floating in water act as self-propelling particles when powered by an external alternating electric field. The millimetre-sized diodes rectify the voltage induced between their electrodes. The resulting particle-localized electro-osmotic flow propels them in the direction of either the cathode or the anode, depending on their surface charge. These rudimentary self-propelling devices can emit light or respond to light and could be controlled by internal logic. Diodes embedded in the walls of microfluidic channels provide locally distributed pumping or mixing functions powered by a global external field. The combined application of a.c. and d.c. fields in such devices allows decoupling of the velocity of the particles and the liquid and could be used for on-chip separations.

Demonstration of Nonpolar m-Plane InGaN/GaN Laser Diodes

Abstract: The first nonpolar m-plane (1-100) nitride laser diodes (LDs) have been realized on low extended defect bulk m-plane GaN substrates The LDs were grown by metal organic chemical vapor deposition (MOCVD) using conditions similar to that of c-plane device growth Broad area lasers were fabricated and tested under pulsed conditions Lasing was observed at duty cycles as high as 10% These laser diodes had threshold current densities (Jth) as low as 75 kA/cm2 Stimulated emission was observed at 4055 nm, with a spectral line-width of 1 nm

Progress in Silicon Single-Photon Avalanche Diodes

Abstract: Silicon single-photon avalanche diodes (SPADs) are nowadays a solid-state alternative to photomultiplier tubes (PMTs) in single-photon counting (SPC) and time-correlated single-photon counting (TCSPC) over the visible spectral range up to 1-mum wavelength. SPADs implemented in planar technology compatible with CMOS circuits offer typical advantages of microelectronic devices (small size, ruggedness, low voltage, low power, etc.). Furthermore, they have inherently higher photon detection efficiency, since they do not rely on electron emission in vacuum from a photocathode as do PMTs, but instead on the internal photoelectric effect. However, PMTs offer much wider sensitive area, which greatly simplifies the design of optical systems; they also attain remarkable performance at high counting rate, and offer picosecond timing resolution with microchannel plate models. In order to make SPAD detectors more competitive in a broader range of SPC and TCSPC applications, it is necessary to face several issues in the semiconductor device design and technology. Such issues will be discussed in the context of the two possible approaches to such a challenge: employing a standard industrial high-voltage CMOS technology or developing a dedicated CMOS-compatible technology. Advances recently attained in the development of SPAD detectors will be outlined and discussed with reference to both single-element detectors and integrated detector arrays.

2-stack 1D-1R Cross-point Structure with Oxide Diodes as Switch Elements for High Density Resistance RAM Applications

Abstract: We have successfully integrated a 2-stack 8times8 array 1D- lR (one diode-one resistor) structure with 0.5 mumtimes0.5 mum cells in order to demonstrate the feasibility of high density stacked RRAM. p-CuOx/n-InZnOx heterojunction thin film was used for the first time as a oxide diode which shows increased current density of two orders over our previous p-NiOx/n-TiOx oxide diode. And Ti-doped NiO was used for the storage node. No limitation to the number of stacks has been observed from our results. Cell and device properties of our cross-point structure 8times8 array are reported. In addition, all fabrication processes were done at room temperature without other dedicated facilities or processes allowing for compatibility with current CMOS technology. Bi-stable switching for 1D-1R memory was demonstrated for our 2-stack cross-point structures showing excellent behavior for both diode and storage nodes. The forward current density for p-CuOx/n-IZOx diodes was over 104A/cm2, and the operation voltage for the storage node with diode attached was around 3 V.

Continuous-Wave Operation of m-Plane InGaN Multiple Quantum Well Laser Diodes

Abstract: Continuous-wave (CW) operation of nonpolar m-plane InGaN/GaN laser diodes (LDs) with the lasing wavelengths approximately 400 nm was demonstrated. The threshold current was 36 mA (4.0 kA/cm2) for the CW operation [28 mA (3.1 kA/cm2) for pulsed mode], being comparable to that of conventional c-plane violet LDs. Both the LDs with the stripes parallel to a- and c-axes showed TE mode operation, according to the polarization selection rules of the transitions in strained InGaN. The c-axis stripe LDs exhibited lower threshold current density, since the lowest energy transition is allowed. As is the case with the m-plane light emitting diodes fabricated on the free-standing m-plane GaN bulk crystals [Okamoto et al.: Jpn. J. Appl. Phys. 45 (2006) L1197], the LDs shown in this paper did not have distinct dislocations, stacking faults, or macroscopic cracks. Nonpolar m-plane GaN-based materials are coming into general use.

A novel monolithic pixelated particle detector implemented in high-voltage CMOS technology ☆

Abstract: A new concept for monolithic pixel detector with 100% fill-factor is presented. The detection is based on the charge collection in the depleted zone of the reverse biased diode. Complex pixel electronics, including charge sensitive amplifier, amplitude discriminator and digital storage element is placed completely inside the diode cathode (N-well). A test chip that comprises a small pixel matrix and test structures has been fabricated in a 0.35 μ m high-voltage CMOS process and successfully tested. The results of the electrical tests and measurements with X-ray and beta radioactive sources are presented.

A New Degradation Mechanism in High-Voltage SiC Power MOSFETs

Abstract: The phenomenon of recombination-induced stacking faults in high-voltage p-n diodes in SiC has been previously shown to increase the forward voltage drop due to reduction of minority carrier lifetime. In this paper, it has been shown that, for the first time, this effect is equally important in unipolar devices such as high-voltage MOSFETs. If the internal body diode is allowed to be forward biased during the operation of these devices, then the recombination-induced SFs will reduce the majority carrier conduction current and increase the leakage current in blocking mode. The effect is more noticeable in high-voltage devices where the drift layer is thick and is not expected to impact 600-1200-V devices.

A Low-Temperature-Grown Oxide Diode as a New Switch Element for High-Density, Nonvolatile Memories†

Abstract: A one-bit cell of a general nonvolatile memory consists of a memory element and a switch element. Several memory elements have been tried given that any bistable states, that is, two charging states, two spin states, or two resistance states, can be used for a memory element. On the other hand, silicon-based transistors have been the most popularly used switch element. However, silicon-based transistors do not conform to high-density, nonvolatile memories with three-dimensional (3D) stack structures due to their high processing temperatures and the difficulty of growing high-quality epitaxial silicon over metals. Here, we show a low-temperaturegrown oxide diode, Pt/p-NiOx/n-TiOx/Pt, applied as a switch element for high-density, nonvolatile memories. The diode exhibits good rectifying characteristics at room temperature: a rectifying ratio of 10 at ± 3 V, a forward current density of up to ∼ 5×10 A cm, an ideality factor of 4.3, and a turn-on voltage of 2 V. Furthermore, we verify its ability to allow and deny access to the Pt/NiO/Pt memory element with two stable resistance states. Under the forward-bias condition, we could access the memory element and change the resistance state, although access was denied under the reverse bias condition. This one-diode/one-resistor (1D/1R) structure could be a promising building block for high-density, nonvolatile random-access memories with 3D stack structures. A p–n diode, like a transistor, is a fundamental circuit element for thin-film electronics. Until now, epitaxial silicon was most frequently used to fabricate p–n diodes in electronic devices with planar structures. However, to increase device density further, we require p–n diodes that are applicable to devices with 3D stack structures. Epitaxial silicon-based p–n diodes cannot be fabricated with stack structures as it is difficult to grow on a metal layer and high processing temperatures are required. On the other hand, although amorphous silicon allows for lower processing temperatures, it does not provide the required semiconducting performance. Therefore, to realize high-density electronic devices with 3D stack structures, we need new p–n diodes composed of semiconducting materials with low processing temperatures and high performance. In particular, new p–n diodes with low processing temperatures and high performance are indispensable to high-density, nonvolatile random-access memory devices. By replacing a transistor with a simpler diode as a switch element, there exists the possibility of producing memory cells with cross-point structures composed of bit lines and word lines perpendicular to each other, with a memory element lying between them. Theoretically, by utilizing this cross-point structure, the cell size can be scaled down to 4F (F: feature size used for patterning the cell), which is the smallest cell size attainable in nonvolatile memories with planar structures. Furthermore, by fabricating 3D stacks of the cross-point structure, the effective cell size can be scaled down to 2F, 1F, and so on. A common issue in realizing a cross-point structure is the availability of a thin-film diode with the high rectifying ratio and current density required for the switch element to access the memory element. Oxide based p–n diodes are good candidates to provide solutions to the issues associated with Si-based diodes. Most oxides, such as TiO2, [4] ZrO2, [5] ZnO, and indium tin oxide (ITO), are well-known n-type semiconductors that are characterized by the electron-transport properties of oxygen vacancies. As NiOx is a well-known p-type semiconductor beC O M M U N IC A IO N

Bridgeless Boost Rectifier With Low Conduction Losses and Reduced Diode Reverse-Recovery Problems

Abstract: A bridgeless boost rectifier with low conduction losses and reduced diode reverse-recovery problems is proposed for power-factor correction. The proposed boost rectifier can reduce the conduction losses and alleviate the diode reverse-recovery problems by using a coupled inductor and two additional diodes. Zero-current turn-off of the output diodes is achieved, and the reverse-recovery currents of the additional diodes are slowed down to reduce the diode reverse-recovery losses. All inductive components are realized on a single magnetic core by utilizing the leakage inductance of the coupled inductor. Furthermore, for the use of this topology in the practical design, the linear peak current mode control is employed for the proposed boost rectifier. A detailed analysis and a control strategy are presented. Experimental results for a 300-W prototype are also discussed to show the performance of the proposed boost rectifier

Rectifier circuit, power supply circuit, and semiconductor device

Abstract: It is an object of the present invention to provide a rectifier circuit that can suppress deterioration or dielectric breakdown of a semiconductor element due to excessive current. A rectifier circuit of the present invention includes at least a first capacitor, a second capacitor, and a diode which are sequentially connected in series in a path which connects an input terminal and one of two output terminals, and a transistor. The second capacitor is connected between one of a source region and a drain region and a gate electrode of the transistor. Further, the other one of the source region and the drain region and the other one of two output terminals are connected each other.

Spin-polarized light-emitting diodes and lasers

Abstract: Spin-polarized light sources are a new class of devices in which the radiative recombination of spin-polarized carriers results in luminescence exhibiting a net circular polarization. The operation principles and design of spin-polarized light sources are discussed. A comprehensive review of experimental work on spin-polarized light-emitting diodes and surface-emitting lasers is provided, concluding with a discussion of future prospects.

Low-voltage operation of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer capacitors and metal-ferroelectric-insulator-semiconductor diodes

Abstract: Exceptionally low-voltage operation of organic ferroelectric capacitors and diodes was demonstrated. Ferroelectric polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] thin films were prepared by the solvent-cast method. Metal-ferroelectric-metal capacitors with 60-nm-thick P(VDF-TrFE) films exhibited well-saturated hysteresis curves whose coercive voltage (Vc) and remanent polarization (Pr) were 2.0V and 11.9μC∕cm2, respectively. The authors also fabricated metal-ferroelectric-insulator-semiconductor diodes with 100-nm-thick P(VDF-TrFE) films. Rectangular-shaped capacitance-voltage (C-V) hysteresis loops were obtained with a voltage sweep range narrower than 5V. The maximum memory window of 4.7V was achieved.

Large-Mass Ultra-Low Noise Germanium Detectors: Performance and Applications in Neutrino and Astroparticle Physics

Abstract: A new type of radiation detector, a p-type modified electrode germanium diode, is presented. The prototype displays, for the first time, a combination of features (mass, energy threshold and background expectation) required for a measurement of coherent neutrino-nucleus scattering in a nuclear reactor experiment. The device hybridizes the mass and energy resolution of a conventional HPGe coaxial gamma spectrometer with the low electronic noise and threshold of a small x-ray semiconductor detector, also displaying an intrinsic ability to distinguish multiple from single-site particle interactions. The present performance of the prototype and possible further improvements are discussed, as well as other applications for this new type of device in neutrino and astroparticle physics (double-beta decay, neutrino magnetic moment and WIMP searches).

Room temperature p-n ZnO blue-violet light-emitting diodes

Abstract: ZnO p-n junction light-emitting diodes (LEDs) were fabricated on c-plane Al2O3 substrates by plasma-assisted molecular beam epitaxy. Gas mixture of N2 and O2 was used as the p-type dopant, by which the double-donor doping of N2(O) can be avoided significantly. The fabricated p-type ZnO layers have a higher hole density and carrier mobility. The LEDs showed a very good rectification characteristic with a low threshold voltage of 4.0V even at a temperature above 300K. The LEDs can even emit intensive electroluminescence in the blue-violet region at the temperature of 350K. The blue-violet emission was attributed to the donor-acceptor pair recombination at the p-type layer of the LED.

A Varactor-Tunable High Impedance Surface With a Resistive-Lumped-Element Biasing Grid

Abstract: A high impedance surface consisting of metallic square patches electrically connected through vias to the ground plane beneath them is made tunable. Tunability is achieved by connecting adjacent patches with varactor diodes thus altering the capacitance between the patches and hence the surface's resonance frequency. The varactor diodes are biased with the aid of a resistive grid. The grid is made resistive using surface mount resistors. Using an approximate equivalent circuit the effect of the varactor diode resistance is investigated for normal plane wave incidence. It is shown that at resonance, a small varactor resistance may lead to a significant absorption. The potential use of a waveguide simulator to characterize approximately the performance of the proposed metamaterial structure is investigated.

CMOS-Compatible All-Si High-Speed Waveguide Photodiodes With High Responsivity in Near-Infrared Communication Band

Abstract: Submicrometer silicon photodiode waveguides, fabricated on silicon-on-insulator substrates, have photoresponse from <1270 to 1740 nm (0.8 AW-1 at 1550 nm) and a 3-dB bandwidth of 10 to 20 GHz. The p-i-n photodiode waveguide consists of an intrinsic waveguide 500times250 nm where the optical mode is confined and two thin, 50-nm-thick, doped Si wings that extend 5 mum out from either side of the waveguide. The Si wings, which are doped one p-type and the other n-type, make electric contact to the waveguide with minimal effect on the optical mode. The edges of the wings are metalized to increase electrical conductivity. Ion implantation of Si+ 1times10 13 cm-2 at 190 keV into the waveguide increases the optical absorption from 2-3 dBmiddotcm-1 to 200-100 dBmiddotcm-1 and causes the generation of a photocurrent when the waveguide is illuminated with subbandgap radiation. The diodes are not damaged by annealing to 450 degC for 15 s or 300 degC for 15 min. The photoresponse and thermal stability is believed due to an oxygen stabilized divacancy complex formed during ion implantation

High-voltage bipolar-cmos-dmos integrated circuit devices and modular methods of forming the same

Abstract: All low-temperature processes are used to fabricate a variety of semiconductor devices in a substrate the does not include an epitaxial layer. The devices include a non-isolated lateral DMOS, a non-isolated extended drain or drifted MOS device, a lateral trench DMOS, an isolated lateral DMOS, JFET and depletion-mode devices, and P-N diode clamps and rectifiers and junction terminations. Since the processes eliminate the need for high temperature processing and employ “as-implanted” dopant profiles, they constitute a modular architecture which allows devices to be added or omitted to the IC without the necessity of altering the processes used to produce the remaining devices.

Ultraviolet semiconductor laser diodes on bulk AlN

Abstract: Current-injection ultraviolet lasers are demonstrated on low-dislocation-density bulk AlN substrates. The AlGaInN heterostructures were grown by metalorganic chemical vapor deposition. Requisite smooth surface morphologies were obtained by growing on near-c-plane AlN substrates, with a nominal off-axis orientation of less than 0.5°. Lasing was obtained from gain-guided laser diodes with uncoated facets and cavity lengths ranging from 200 to 1500 μm. Threshold current densities as low as 13 kA/cm2 were achieved for laser emission wavelengths as short as 368 nm, under pulsed operation. The maximum light output power was near 300 mW with a differential quantum efficiency of 6.7%. This (first) demonstration of nitride laser diodes on bulk AlN substrates suggests the feasibility of using such substrates to realize nitride laser diodes emitting from the near to deep ultraviolet spectral regions.

High speed silicon photonic crystal waveguide modulator for low voltage operation

Abstract: A high speed compact silicon modulator is experimentally demonstrated to work at a low driving voltage desirable for on-chip applications. As carrier injection is the only practical option for optical modulation in silicon, a lower limit of current density (∼104A∕cm2) exists for achieving gigahertz modulation in the p-i-n diode configuration. Exploiting the slow group velocity of light in photonic crystal waveguides, the interaction length of this Mach-Zehnder interferometer-type silicon modulator is reduced significantly compared to conventional modulators. The required high current density is achieved with a low voltage (2V) by scaling down the interaction length to 80μm.

Demonstration of high power blue-green light emitting diode on semipolar (1122) bulk GaN substrate

Abstract: Blue-green InGaN/GaN multiple-quantum-well light emitting diodes with peak emission wavelength of 480 nm were grown on low extended defect density semipolar (1122) bulk GaN substrates by conventional metal organic chemical vapour deposition. The calculated external quantum efficiency and output power at a drive current of 20 mA under pulsed operations (10% duty cycle) were 18% and 9 mW, respectively. The device exhibited small electroluminescence wavelength shift (4.5 nm) with drive currents ranging from 30 to 100 mA, indicating significant reduction of polarisation-related internal electric fields.

High-performance nano-Schottky diodes and nano-MESFETs made on single CdS nanobelts.

Abstract: Nano-Schottky diodes and nanometal-semiconductor field-effect transistors (MESFETs) on single CdS nanobelts (NBs) have been fabricated and studied. The Au/CdS NB Schottky diodes have very low reverse current density ( approximately 3.0 x 10-5 A.cm-2 at -10 V reverse bias) and the highest on/off current ratio (approximately 108) reported so far for nano-Schottky diodes. The single CdS NB MESFETs exhibit n-channel normally on (depletion) mode, low threshold voltage (approximately -1.56 V), high transconductance ( approximately 3.5 microS), low subthreshold swing ( approximately 45 mV/dec), and the highest on/off current ratio (approximately 2 x 108) reported so far for nanofield-effect transistors. We also show that the absolute value of threshold voltage for a metal-insulator-semiconductor field-effect transistor made on a single CdS NB can be reduced from approximately 12.5 to approximately 0.4 V and its transconductance can be increased from approximately 0.2 to approximately 3.2 microS by adding an extra Au Schottky contact on the CdS NB, the mechanism of which is discussed.

Polyelectrolyte Diode: Nonlinear Current Response of a Junction between Aqueous Ionic Gels

Abstract: We demonstrate that a fixed junction between two aqueous gels containing oppositely charged polyelectrolytes could rectify electric current. The agarose-based gels were “doped” with sodium poly(styrene sulfonic acid) and poly(diallyl dimethylammonium chloride). The unidirectional current response of the interface between the cationic and anionic gels originates directly from anisotropy in the mobile ionic charges in the gels. The current depends on the concentration of polyelectrolyte, the background ionic concentration, and the distance traveled by the ions. The I−V curves from the devices demonstrated a combination of transient and stationary rectification effects. The current densities achieved were comparable to or higher than those obtained with previously reported organic semiconductor diodes. The diodes had good long-term stability in both DC and AC conduction modes. The materials and the process of preparation of these devices are simple, inexpensive, and scalable. They could be used in flexible a...

ZnO-on-GaN heterojunction light-emitting diode grown by vapor cooling condensation technique

Abstract: The growth of ZnO-on-GaN heterostructures was implemented using the vapor cooling condensation system. The technique thus developed was employed to fabricate both the p-GaN∕n-ZnO:In (p-n) and p-GaN∕i-ZnO∕n-ZnO:In (p-i-n) heterojunction light-emitting diodes (LEDs). A rectifying diodelike behavior was clearly observed from both the p-n and p-i-n heterojunction LEDs, with the forward turn-on voltage of 3V and the reverse breakdown voltage of −15V determined for the p-n heterojunction LEDs, compared to 7 and −23V, respectively, for the p-i-n heterojunction LEDs. Based on the results of photoluminescence and electroluminescence studies conducted on these LED structures, the ZnO layer responsible for the peak emission wavelength of 385nm were also verified experimentally.

Negative capacitance in organic semiconductor devices: Bipolar injection and charge recombination mechanism

Abstract: The authors report negative capacitance at low frequencies in organic semiconductor based diodes and show that it appears only under bipolar injection conditions. They account quantitatively for this phenomenon by the recombination current due to electron-hole annihilation. Simple addition of the recombination current to the well established model of space charge limited current in the presence of traps yields excellent fits to the experimentally measured admittance data. The dependence of the extracted characteristic recombination time on the bias voltage is indicative of a recombination process which is mediated by localized traps.

Responsivity and Noise Measurements of Zero-Bias Schottky Diode Detectors

Abstract: Schottky barrier diodes can be used as direct detectors throughout the millimeterand submillimeterwave bands. When the diodes are optimized to have a low forward turn-on voltage, the detectors can achieve excellent frequency response and bandwidth, even with zero-bias. This paper reports on the characterization of VDI’s zerobias Schottky detectors. Responsivity typically ranges from 4,000 V/W at 100 GHz to 400 V/W at 900 GHz and each detector achieves good responsivity across the entire singlemoded bandwidth of the input rectangular waveguide. Under low power operation the detectors achieve a measured noise-equivalent-power (NEP) of about 1.5x10 W/√Hz, even without signal modulation. Such high sensitivity is expected for any zero-bias diode detector with high responsivity when there is no incident RF power; since only thermal noise can be generated under this condition. However, as the input power is increased, excess noise is generated. This noise typically has a 1/f power spectrum and is commonly known as flicker noise. Flicker noise becomes increasingly important as the input power is increased and signal modulation is generally required to achieve maximum sensitivity. The signal-to-noise of the VDI zero-bias detectors has been carefully measured as a function of input power and modulation rate. This data allows the user to understand the sensitivity of the detector under real operating conditions, and is therefore far more useful than the simple measurement of detector NEP with zero RF power, which is commonly quoted in the literature for new diode detector designs. Index Terms — Terahertz detectors, zero-bias detectors, noise-equivalent power, flicker noise.

Laser obstacle ranging and display

Abstract: Apparatus, for detecting at least one object and preventing receiver burn-out, mounted on a vehicle, including a laser and at least one receiver, the receiver being coupled with the laser, the laser for transmitting a beam of light and the receiver for detecting reflections of the beam of light from the object, the laser including at least one signal diode, a commutator, a power supply signal diode driver, a circulator, an erbium doped fiber (EDF), a wavelength division multiplexer (WDM), a narrow band Bragg reflector, a first fiber pump diode, an output combiner and a second fiber pump diode, the commutator being coupled with each signal diode and the power supply signal diode drive, the circulator being optically coupled with each signal diode, the EDF and the output combiner, the WDM being optically coupled with the EDF, the narrow band Bragg reflector and the first fiber pump diode and the second fiber pump diode being optically coupled with the output combiner, each signal diode generating a beam of light distinct from one another, the power supply signal diode driver for supplying energy to each signal diode, the circulator for directing the beam of light in at least one of at least two different directions, the EDF for amplifying the beam of light thereby producing an amplified beam of light, the narrow band Bragg reflector for reflecting only the amplified beam of light through the EDF a second time, thereby producing a double amplified beam of light and the first fiber pump diode and the second fiber pump diode for pumping the EDF, wherein the WDM and each of the signal diodes are located on opposite sides of the EDF, wherein the output combiner outputs the beam of light, wherein the commutator enables each signal diode, one at a time, to draw a predetermined amount of energy from the power supply signal diode driver, wherein one signal diode generates a low energy beam of light and another one generates a high energy beam of light, wherein the low energy beam of light is transmitted by the output combiner before the high energy beam of light, and when the low energy beam of light is detected by the receiver, and the energy level of the low energy beam is above a predetermined threshold, the high energy beam of light is not transmitted.

Analytic findings in the electroluminescence characterization of crystalline silicon solar cells

Abstract: The electroluminescence intensity from Si cells under the forward bias was found to have one to one quantitative agreement with the minority carrier diffusion length. Based on the diffusion equation and simple p-n diode model, the electroluminescence intensity was analyzed relative to the cell performance. Electroluminescence intensity is proportional to the product of the injected minority carrier density and the effective diffusion length. The diode ideality factor n can be deduced by measuring the electroluminescence intensity as a function of the forward injection current. Among various crystalline silicon cells including single and polycrystalline types, the measured electroluminescence intensity at a fixed forward current has a tight relationship with the open circuit voltage of each cell, which gives a very convenient way to evaluate cell performance.