Diode Temperature Research Articles

PIN diodes for radiation therapy use: Their construction, characterization, and implementation

PurposeDevelopment and implementation of a PIN diode measurement system that can measure dose on the surface of a patient, which can be compared to dose calculated by a treatment planning system. Measurements are to be possible for static or rotational photon beams and electrons. Simple calibration procedures are to be devised that require a minimum set of correction factors. MethodsReadily available PIN type photodiodes are fabricated into devices that can be used for detection of ionizing radiation. Single or dual PIN diodes are soldered onto flexible shielded cables for static and rotational irradiation use. Diode signals are measured with an electrometer with zero input bias voltage. Diode temperature is determined by operating it as a thermistor. Linac photon and electron dose is measured. A commercial treatment planning system is used for calculating dose expected in various test geometries. ResultsThe scanning and surface diodes have an intrinsic buildup of 0.3 mm water equivalence and the IMRT device a buildup of 1.5 mm. Correction factors are determined for changes in diode sensitivity with the following factors: dose-per-pulse, dose rate, angle of radiation incidence, temperature, and field size. The surface or IMRT diode detector measurements agree within 1.0% with Eclipse calculations. ConclusionsClinically useable dose detection devices can be fabricated from PIN type photodiodes. These diodes are used to measure dose at the surface of a patient or under bolus. Correction factors are unnecessary if a surface or IMRT type device is chosen for use with static orthogonal or rotational IMRT delivered beams, respectively.

High Temperature Operation Limit Assessment for 4H-SiC Schottky Diode-Based Extreme Temperature Sensors

We developed a simplified theoretical model for parameters calculation of diode temperature sensors (DTS) based on Schottky diodes (SD). The current flow mechanism of the diodes considered was dominated by over-barrier thermionic emission. Qualitative correlations between basic fundamental and electrophysical parameters of such DTS were established. The expressions for ultimate high-temperature parameters of the DTS were obtained. Theoretical results obtained were approved using the test samples of DTS with Schottky contact Ni/n-SiC (4H). It was shown that physical high-temperature limit of operation of such a DTS (>1250 K) exceeded the values of commercial DTS based on Si, GaAs, and AlGaAs p-n junctions. And the SD-based DTS itself demonstrated significantly lower energy consumption.

Wide-Range, Open-Loop, CCT and Illuminance Control of an LED Lamp Using Two-Component Color Blending

This paper proposes a wide-range control scheme of correlated color temperature (CCT) and illuminance of a light-emitting diode (LED) lamp, using two-component color blending. A simple control algorithm is implemented by using Grassmann's law of color mixing and McCamy's formula of CCT. Light from a white LED source is blended with that from a blue LED or a red LED to get, respectively, a CCT value higher or lower than that of the white CCT. The prototype LED lighting system can independently produce a variable CCT ranging from 2500 to 12500 K and a variable illuminance ranging from 5 to 120 lx. The algorithm is experimentally validated by hardware implementation. An empirical model to estimate the luminous parameters of the individual LED is also implemented. Experimental results show that although the system is an open-loop one, it is quite accurate with respect to set point CCT and illuminance. Despite acceptable performance in respect of these two quantities, a large deviation from the color of an ideal black body radiator is noticeable in a part of the CCT range, and a remedy of the problem has been suggested.

Development of diode temperature sensors with operating range up to 750 K

The problem of expansion of the range of functioning of diode thermosensors in the region of high temperatures is considered and some of the results of the author’s research in this area are given. To solve this problem, it is proposed to use diode structures based on wide bandgap semiconductor compounds in the III-V system. The technological method of producing prototypes of high-temperature diode temperature sensors based on GaP is developed. The presented method allows manufacturing samples of diode temperature sensors, the high-temperature limit of which exceeds the limit of functioning of commercial silicon diode temperature sensors by about 200–300 K. The experimental methods of obtaining epitaxial structures of solid solutions of AlGaAs and fabricating diode temperature sensors based on them are developed. It is shown that the approach chosen in this work allows extending the thermometric characteristics of such diodes in the high-temperature region by approximately 150–250 K. The paper presents the methodology for forming InGaN device structures and production of prototype high-temperature diode temperature sensors based on them. This technique with revisions can be used for the manufacture of diode temperature sensors and other devices for high-temperature applications, the entire range of solid solutions in the InN-GaN system. The parameters and characteristics of the obtained diode temperature sensors are investigated. The results of the research can be used by specialists in the field of electronics and optoelectronics in the development and production of semiconductor devices.

Experimental studies of 1.5 – 1.6 μm high-power asymmetric-waveguide single-mode lasers

The current – voltage, power – current, and spectral characteristics of high-power single-mode semiconductor lasers emitting at wavelengths of 1.5 – 1.6 μm are studied experimentally. It is shown that a laser with a cavity length of 1.6 mm and a mesa-stripe width of 3 μm mounted in a housing 11 mm in diameter may emit a power higher than 300 mW. Mounting of lasers on C-mounts makes it possible to achieve powers exceeding 400 mW. In the case of mounting in standard 14 pin DIL packages, the laser power at the exit of a single-mode fibre-optic cable (FOC) was no lower than 100 mW, which, taking into account 50 % losses upon radiation coupling into the FOC, corresponds to the laser diode power higher than 200 mW. It is shown that the differential resistance of a laser depends not only on the laser crystal length but also on the type of mounting (in copper housings 11 mm in diameter or on C-mounts). The dependences of the laser wavelength and spectral width on the pump current and ambient temperature are presented. The characteristic temperatures of laser diodes are determined.

Thermal model of the IGBT module

In the paper the dynamic compact thermal model of the IGBT module is proposed. This model makes it possible to calculate internal temperatures of diodes and transistors included in the considered IGBT module with selfheating in each device and mutual thermal couplings between them taken into account. The form of this model and the method of estimation of its selected parameters are described. Some results of measurements and calculations illustrating the usefulness of this model are shown and discussed.

Strong light illumination on gain-switched semiconductor lasers helps the eavesdropper in practical quantum key distribution systems

The temperature of the semiconductor diode increases under strong light illumination whether thermoelectric cooler is installed or not, which changes the output wavelength of the laser (Lee et al., 2017). However, other characteristics also vary as temperature increases. These variations may help the eavesdropper in practical quantum key distribution systems. We study the effects of temperature increase on gain-switched semiconductor lasers by simulating temperature dependent rate equations. The results show that temperature increase may cause large intensity fluctuation, decrease the output intensity and lead the signal state and decoy state distinguishable. We also propose a modified photon number splitting attack by exploiting the effects of temperature increase. Countermeasures are also proposed.

High temperature diode sensors based on InGaN/AlGaN structures

The authors have established the factors defining the maximum temperature limit of operating as well as the thermal sensitivity of the diode temperature sensors based on double heterostructures InGaN/AlGaN in a condition when tunnel current flow prevails. The authors have obtained analytic dependencies for the maximum temperature and sensitivity and have analyzed a connection of these characteristics with the parameters of the semiconductor material and the diode structure. In particular, it was shown that the sensitivity did not depend on the diode sensor operation current and, in the case of double heterostructure, its value was proportional to the energy gap difference of the heterojunction. Relying on the experimental data, the authors state that to design a diode temperature sensor possessing maximum values of operation temperature and thermal sensitivity at minimal operation current, it is necessary to utilize double heterostructures based on wide bandgap semiconductors. Base and emitter layers of the structure should be heavily doped. The optimal value of the energy gap difference between active and confining layers of about 0.2–0.3 eV should be provided. In addition, in the double heterostructure chosen, the tunnel transport of the charge carriers with smaller effective mass should dominate.

Thermal Analysis of Blue Laser Diode for Solid State Lighting Application

Solid-state light sources based on laser diode are becoming great alternative for LEDs. Improvement of the thermal characteristics of InGaN LD is very important for realizing reliable devices. In this investigation the influence of the temperature of diode on light parameters was studied. White light was obtained by coupling blue light of diode with yellow phosphors: YAG:Ce3+ and GYAG:Ce3+ with nitride. For three values of the temperature of LD’s stem, regulated by Peltier module, CCT, CRI and chromaticity coordinates were measured by spectroradiometer. The importance of emission characteristics of materials was shown. Subsequently, the influence of temperature on laser diode intensity was investigated for 120 hours. This experiment was repeated for different levels of current and temperature. Finally, the steady state of thermal finite element analysis was performed to reveal the distribution of the temperature. The analysis showed the importance of heat sink and also temperature control.

Iodine-stabilized single-frequency green InGaN diode laser.

A 520-nm InGaN diode laser can emit a milliwatt-level, single-frequency laser beam when the applied current slightly exceeds the lasing threshold. The laser frequency was less sensitive to diode temperature and could be finely tuned by adjusting the applied current. Laser frequency was stabilized onto a hyperfine component in an iodine transition through the saturated absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8×10-9 at a 10-s integration time. This compact laser system can replace the conventional green diode-pumped solid-state laser and applied as a frequency reference. A single longitudinal mode operational region with diode temperature, current, and output power was investigated.

Large scale production of densified hydrogen to the triple point and below

Recent demonstration of advanced liquid hydrogen storage techniques using Integrated Refrigeration and Storage technology at NASA Kennedy Space Center led to the production of large quantities of densified liquid and slush hydrogen in a 125,000 L tank. Production of densified hydrogen was performed at three different liquid levels and LH2 temperatures were measured by twenty silicon diode temperature sensors. Overall densification performance of the system is explored, and solid mass fractions are calculated. Experimental data reveal hydrogen temperatures dropped well below the triple point during testing, and were continuing to trend downward prior to system shutdown. Sub-triple point temperatures were seen to evolve in a time dependent manner along the length of the horizontal, cylindrical vessel. The phenomenon, observed at two fill levels, is detailed herein. The implications of using IRAS for energy storage, propellant densification, and future cryofuel systems are discussed.

Determination of Ultimate Output Characteristics of Wide Bandgap Recombination-Mode Diode Temperature Sensors

Criteria of electric and electrophysical parameters selection for recombination-type diode temperature sensors (DTS) based on p+–n or n+–p structures of wide bandgap semiconductor materials were developed. The set of such parameters enables to provide either maximum length of a temperature response curve (TRC) or maximum thermal sensitivity of the DTS. For the DTS based on epitaxial p+–n GaP structures the boundary positions of the TRC were simulated in the correlation with its thermal sensitivity. The comparison with experiment showed that the TRCs measured of GaP DTS were in the range limited by the simulated extreme characteristics.

A Reliability Prediction for Integrated LED Lamp With Electrolytic Capacitor-Free Driver

This paper studies the interaction of catastrophic failure of the driver and LED luminous flux decay for an integrated LED lamp with an electrolytic capacitor-free LED driver. Electronic thermal simulations are utilized to obtain the lamp’s dynamic history of temperature and current for two distinct operation modes: constant current mode (CCM) and constant light output (CLO) mode, respectively. Driver’s mean time to failure (MTTF) and the LED’s lifetime in terms of luminous flux are calculated. Under CLO mode, the LED’s current increases exponentially to maintain the constant light output. As a result, the junction temperatures of LEDs, MOSFETs, and power diodes in driver rise significantly, leading to a much shorter MTTF and faster luminous flux depreciation. However, under the CCM, the junction temperatures of LEDs, MOSFETs, and diodes change modestly; therefore, the driver’s MTTF and LED’s luminous flux decay are not affected much by the variation of temperatures during LED’s degradation process.

ENR Compensation of a Noise Source Using Calibration Coefficients With Variation of the Ambient Temperature

The excess noise ratio (ENR) of a noise source is largely dependent on the ambient temperature variation. In this paper, we discuss a method to compensate for the ENR of a noise source with respect to ambient temperature variations. From the measured quantities of the receiver and noise source from the setup, calibration coefficients of the noise source are extracted according to the relationship between bias voltage at the noise diode, the ENR, and the physical temperature of noise diode in the noise source by means of a least square estimation. From the result, the ENR of the noise source is compensated by the bias voltage at the noise diode controlled by a microcontroller and a digital-to-analog converter in the noise source. The compensated ENR variation is 0.167 dB for 1.4 dB ENR at 5.4 GHz in an ambient temperature range of 290–320 K. Specifically, the calibrated noise source shows the characteristics of 0.0016 dB/° C in a short ambient temperature range of 310–320 K. The time stability is about 0.007 dB/h for 1.4 dB ENR at 5.4 GHz. The uncertainty is evaluated in the experimental results, and the critical uncertainty contribution is confirmed by reading the power from a spectrum analyzer.

Photovoltaics in the shade: one bypass diode per solar cell revisited

Deployment of residential photovoltaic solar energy systems is strongly increasing, which gives rise to problems such as partial shading and pollution, omnipresent in the built environment. Conventional modules are sensitive to the current mismatches introduced by shadows because of their series architecture of electrical interconnections. This paper presents simulations and experiments showing that a new generation of bypass diodes (BPDs) can be used, up to 1 BPD per cell, to improve the shading tolerance of conventional crystalline modules. We have used cardboard of 0% transmission, and a wire mesh (net) of 38% transmission. The more BPDs are used, the higher the maximum power under shading conditions. Using 20 smart BPDs, or 1 BPD per three cells, leads to an improvement of a factor 3 in power output; for our netting experiments, a factor 1.5 is found. Both performance enhancement and lower diode temperatures lead to increased shade resilience and reliability. © 2017 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.

Measurement of the water content in oil and oil products using IR light-emitting diode–photodiode optrons

The feasibility of using light-emitting devices, the radiation spectrum of which has maxima at wavelengths of 1.7, 1.9, and 2.2 μm for determining the water concentration in oil and oil products (gasoline, kerosene, diesel fuel) has been demonstrated. It has been found that the measurement error can be lowered if (i) the temperature of the light-emitting diode is maintained accurate to 0.5–1.0°C, (ii) by using a cell through which a permanently stirred analyte is pumped, and (iii) by selecting the repetition rate of radiation pulses from the light-emitting diodes according to the averaging time. A meter of water content in oil and oil products has been developed that is built around IR light-emitting device–photodiode optrons. This device provides water content on-line monitoring accurate to 1.5%.

Phosphor Temperature Overestimation in High-Power Light-Emitting Diode by Thermocouple

Phosphor temperature in high-power white light-emitting diodes can greatly affect the optical properties, reliability, and lifetime. Accurate estimation of phosphor temperature is the first step for enhancing thermal management inside the package. In this paper, the phosphor temperature was measured by a plug-in method with thermocouple. The thermocouple’s bead was inserted into the phosphor layer, and then the silicone matrix got cured. The phosphor temperature was measured under various input currents. Under 350 mA, the temperature difference between the measured value and the junction temperature was about 17 °C higher than those in the references. The reason for this overestimation was attributed to light energy absorption and conversion of the bead, which was confirmed by thermal simulations.

Efficiency analysis of 808 nm laser diode array under different operating temperatures

The 808 nm high-efficiency laser diodes have many advantages, such as high output power, high reliabilities, compact sizes, which are widely used in many areas, such as industry, communication, science, medicine and biology. In order to improve the power conversion efficiencies of 808 nm laser diodes, the following requirements must be considered, such as loss of joule heating, loss by the carrier leakage, spontaneous radiation loss below the threshold current, loss by interface voltage defect, internal losses including free-carrier absorption loss and scattering loss. These losses above are closely related to the operating temperature of laser diode. In this paper, power conversion efficiency analysis is demonstrated from the aspects of the output power, threshold current, slope efficiency, voltage, and series resistance at different temperatures.. This is the first time that the detailed study has been carried out under various temperatures (up to the lowest temperature of -40℃). And the detailed study above can be of benefit to designing the wafer epitaxial structure. High-power 808 nm laser diode arrays are mounted on conduction cooled heatsinks. And the laser chips have 47 emitters with 50% in fill factor, 100 m stripe in width and 1.5 mm in cavity length. The asymmetric broad waveguide epitaxial structure with lower absorption loss in p-type waveguide and cladding layer is designed in order to reduce the internal losses. The device performances are measured under operating temperatures ranging from -40℃ to 25℃ including the output power, threshold current, slope efficiency, series resistance, voltage, etc. Then the power conversion efficiency of 808 nm laser diode arrays are demonstrated from the output characteristics at different operating temperatures. With temperature decreasing, the series resistance gradually increases. The loss of joule heating ratio rises from 7.8% to 10.3%. In that case, the high series resistance is the major factor to prevent the efficiency from further improving at a low temperature of -40℃. As temperature decreases from 25℃ to -40℃, the carrier leakage ratio is reduced from 16.6% to 3.1%, the carrier leakage is the dominant factor for increasing efficiency, which means that it is necessary to optimize the epitaxial structure in order to reduce the carrier leakage at the room temperature. Comparing the two different work temperatures from -30℃ to -40℃, the carrier leakage ratio only changes 0.1%, which implies that the carrier leakage could be ignored under the low temperature. Meanwhile, as temperature decreases from 25℃ to -40℃, the power conversion efficiency increases from 56.7% to 66.8%.

Negative characteristic temperature of GaN-based blue laser diode investigated by numerical simulation

GaN-based blue laser diodes (LDs) may exhibit anomalous temperature characteristics such as a very high or negative characteristic temperature (T 0). In this work, the temperature characteristics of blue LDs having InGaN double quantum-well (QW) active region are investigated using numerical simulation. It is found that the T 0 is greatly influenced by the n-type doped barrier between the QWs and a negative T 0 can be observed for the LD structure with a heavily doped barrier. The negative T 0 of InGaN blue LDs is mainly attributed to the decrease of the Auger recombination rate at the p-side QW with increasing temperature as a result of the thermally enhanced hole transport from the p-side to the n-side QW.

Evaluation of antimicrobial and thermal effects of diode laser on root canal dentin

The aim of this study was to evaluate the antimicrobial effects of diode laser and temperature rise on the root surface during application. Thirty-six teeth were chemomechanically prepared and irrigated with 2.5% sodium hypochlorite and 17% ethylenediaminetetraacetic acid, and then autoclaved and incubated with a suspension of Enterococcus faecalis. The specimens were randomly divided into three groups (n = 12): Group 1, irradiated by diode laser at 1.2 W; Group 2, irradiated by diode laser at 2 W; and Group 3, irradiated by diode laser at 3 W. The grown bacteria were counted and the mean numbers of the each test tube were determined. The temperature was measured on the external apical third of the root during laser application. The mean values of results for each group were compared using one-way analysis of variance and Tukey test. No significant difference was obtained among the test groups in terms of the colony counts (P > 0.05). According to the temperature changes, there was a significant difference between groups (P < 0.05). Temperature rises were 16.79°C, 10.20°C, and 6.25°C in Group 3, Group 2, and Group 1, respectively. Diode laser irradiation with 1.2 W demonstrated comparable performance with 2 W and 3 W power sets for elimination of E. faecalis from root canal with less temperature rise.