AlGaAs Light-emitting Diodes Research Articles

Optoelectronic Measuring Systems for High-Voltage Installations Based on Photovoltaic Converters

We consider the main principles of construction of optoelectronic measuring systems in which the electric power supply of measuring modules is realized with the help of optical emission transmitted through a fiber light-guide. We present various versions of manufacturing of simple photovoltaic converters with a conversion efficiency of up to 50% based on the photodiode assemblies and AlGaAs light-emitting diodes. The factors limiting the power supplied by the optical emission are analyzed. The possibilities of realization of measuring modules based on self-excited generators with resistive and capacitive transducers based on multichannel analog-to-digital converters are presented. The methods aimed at decreasing the energy consumption of the measuring modules are analyzed.

Optically Powered Optical Transmitter Using a Single Light-Emitting Diode

An optically powered optical transmitter using a single light-emitting diode (LED) is presented with a batteryless and low-power temperature sensor node. The commercially available AlGaAs LED has higher open-circuit voltage (~1.2 V) than CMOS photodiode (~0.5 V), such that an analog/mixed signal design in 0.18- $\mu \text{m}$ process can be powered directly without losing efficiency to a sustained voltage boosting scheme. Higher voltage is needed only during brief transmissions. A scalable, inverter-based, switched capacitor voltage boosting transmitter drives the LED in short pulses with 93% electrical energy efficiency. Three consecutive pulses are sent as preamble symbol, two as logic 0 and one as logic 1. The microsystem features a $\Delta V_{{\text {BE}}}$ -based temperature sensor with a data-dependent partial conversion scheme to save energy. The sensor expends 1 nJ/full conversion at 5 kSa/s and 0.25 nJ/partial conversion at 20 kSa/s. The transmitter can serially output data at 1 nJ/pulse; 10-cm detection distance is achieved under 6-mW/mm2 light intensity using an in-house photodiode detector circuit. The circuitry dissipates 6 $\mu \text{W}$ in total at 1.2-V nominal voltage. It consists of a 0.1-mm2 LED die, 2.25-mm2 IC, and a surface mounted device storage capacitor, taking approximately 1-mm3 volume.

Optical upconverter with integrated heterojunction phototransistor and light-emitting diode

We report an optical upconversion device that converts input 1.5μm light to output 0.87μm light with a built-in gain mechanism. The device consists of an InGaAs∕InP heterojunction phototransistor (HPT) integrated with a GaAs∕AlGaAs light-emitting diode (LED) by wafer fusion process. Incoming 1.5μm optical radiation is absorbed by the HPT, generating an amplified photocurrent. The resultant photocurrent drives the LED that emits at 0.87μm, which could be detected by a conventional silicon charge-coupled device. Upconversion is demonstrated at room temperature with a gain of 20 from the HPT and an overall external upconversion efficiency of 0.07W∕W.

Midinfrared optical upconverter

We have developed a midinfrared optical upconverter by wafer bonding a GaAs∕AlGaAs light-emitting diode with an InSb p+nn+ photodetector. The device converts midinfrared radiation in the range of 3–5.45μm to near-infrared light at 0.84μm, which can be efficiently detected using a widely available Si charge coupled device. At 77K, the measured external upconversion efficiency was 0.093W∕W. The optical up-conversion device, in combination with the Si CCD camera, leads to an alternative solution for making low-cost and large-area midinfrared imaging device. Effects of electrical gain and photon recycling inside this integrated device are discussed.

Optimized GaAs∕AlGaAs light-emitting diodes and high efficiency wafer-fused optical up-conversion devices

Achieving a high internal quantum efficiency in GaAs∕AlGaAs based light-emitting diodes (LEDs) for room-temperature operation at low current-density injection is crucial for applications such as optical up-converters based on the integration of LEDs and photodetectros. We report the experimental results as well as the theoretical analyses of the internal quantum efficiency of GaAs∕AlGaAs LEDs as a function of the p-doping concentration of the active region for low current injection operation. By optimizing the doping concentration, we have achieved a close to 100% internal quantum efficiency for room-temperature operation of LEDs in the low injection current-density range, i.e., around 0.1A∕cm2. An optical up-converter was fabricated using wafer-fusion technology by integrating the optimized GaAs∕AlGaAs LED with an InGaAs∕InP photodetector. The internal up-conversion quantum efficiency was measured to be 76%.

Energy dependence of proton damage in AlGaAs light-emitting diodes

We measure the energy dependence of proton-induced LED degradation using large numbers of devices and incremental exposures to gain high confidence in the proton energy dependence and device-to-device variability of damage. We compare single versus double heterojunction AlGaAs technologies (emitting at 880 nm and 830 nm, respectively) to previous experimental and theoretical results. We also present a critical review of the use of nonionizing energy loss in AlGaAs for predictions of on-orbit degradation and assess the uncertainties inherent in this approach.

Wide-band suppression of photon-number fluctuations in a high-speed light-emitting diode driven by a constant-current source

We demonstrate experimental results on the generation of sub-Poissonian photon fluxes emanating from an AlGaAs light-emitting diode, which manifest a wide-band (0–100 MHz) noise suppression below the standard quantum limit level despite low current density (∼38 A/cm2) operation at room temperature. The experimental noise power spectrum is well fitted in terms of the theoretical curve estimated with the quantum mechanical Langevin equations.

Bulk lifetime determination in high purity silicon by contactless laser technique

The result of bulk lifetime measurements in high purity silicon are presented. For this investigation we offer a new method and technique for determination of the bulk value of the excess carrier lifetime in high purity silicon. The effective value of the lifetime being measured in such a material depends on the dimensions of the ingot. In our method the sample to be investigated is illuminated by the modulated radiation of the AlGaAs light-emitting diode (LED), which generates the excess carriers, and by the probe beam of the He-Ne laser (λp = 3.39 μm), which becomes modulated when passing through the sample. The bulk lifetime is determined by the analysis of the dependence of the phase shift between these two modulations versus the distance r between the points on the sample surface illuminated by the sources.

An application of spectroscopic emission microscopy and cathodoluminescence to the failure analysis of near-infrared light emitting diodes

Spectroscopic emission microscopy and cathodoluminescence have been applied to analyze the mechanism causing light output degradation in AlGaAs infrared light emitting diodes (LEDs). Using a spectroscopic emission microscope which was put together in-house, the emission properties of the AlGaAs LEDs under forward bias were analyzed before and after device decapsulation. Monochromatic cathodoluminescence (CL) microscopy was used to further analyze the near-surface AlGaAs epitaxial layer. Since the information provided by the cathodoluminescence method is limited by the penetration depth of the incident electrons, the emission images are useful in revealing information that is close to the pn junction. This is especially so for deep junctions which are very difficult to assess using an electron probe. Crystalline defects at and in the vicinity of the junction, and defects near the surface can be separated using a combination of emission microscopy and cathodoluminescence techniques. The emission microscope, equipped with both spectroscopic and imaging capabilities, has found applications in the study of the emission properties of light emitters.

Kinetics of red AlGaAs light-emitting diodes degradation

The kinetics of the gradual degradation of red AlGaAs light-emitting diodes (LED) has been studied. This degradation has been shown to be due to diffusion of Zn atoms from the GaAs substrate to the p-n+ junction. The gradual degradation kinetics has been described on the basis of a diffusion model. It has been ascertained that the Zn atom diffusion process is not recombination-enhanced. At the same time the process of elastic stress relaxation, occuring at the initial stage of the LED degradation, is enhanced by the flowing current.

High performance AlGaInP visible light-emitting diodes

The performance of surface-emitting visible AlGaInP light-emitting diodes (LEDs) is described. The devices have external quantum efficiencies greater than 2% and luminous efficiencies of 20 lm/A in the yellow (590 nm) spectral region. This performance is roughly ten times better than existing yellow LEDs and is comparable to the highest performance red AlGaAs LEDs currently available. The devices also perform favorably compared to existing devices in the orange and green spectral regions. Low-pressure organometallic vapor phase epitaxy (OMVPE) is used to grow the epitaxial layers. The devices consist of a double heterostructure with an AlGaInP active region grown on a GaAs substrate.

Recombination-enhanced transformation of deep centers in red light-emitting AlGaAs diodes

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Planar monolithic integration of LED and FET devices on a conductive substrate

This paper describes results of a study on the monolithic integration of AlGaAs light-emitting diodes with GaAs field-effect transistors on a conductive p-GaAs substrate. Using a selective growth technique, a horizontal configuration is fabricated that allows separate optimization of the two types of devices and provides a quasi-planar surface. This approach is compatible with the standard GaAs integrated-circuit technology. By inserting an undoped layer and a p-n junction between the active layer of the FET and the substrate leakage currents below 500 µA for bias voltage up to 9 V are obtained for these insulation structures. The emitted light intensity of the LED, connected in series with the FET, exhibits a nearly linear dependence on the driving gate potential. Temperature or optical crosstalk effects were not observed. Fall and rise times around 20 ns were measured from the pulse response characteristics. This switching time is limited by the LED whereas the FET and isolation layers were found not to affect the switching behavior of the circuit in this time frame.

Integrated optical fiber data link transmitter/receiver for local area network application

Abstract Optical fiber data link transmitters and receivers have been developed for local area network applications. The features are of wide-bit-rate range and wide dynamic range as well as compact and of highly reliable construction. State-of-the-art LSI technology has been applied for the circuit electronics integration. Design emphasis was also placed on the optical connector development for ease of operation as well as reliable connection and compact size. The data link transmitter and receiver developed utilize an AlGaAs light-emitting diode and a Si PIN photodiode as the light source and detector, respectively. Performance data were obtained for a bit rate range of dc to 35 Mbps and an 18–dB dynamic range.