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Y Xi - One of the best experts on this subject based on the ideXlab platform.

  • junction temperature in ultraviolet light emitting diodes
    Japanese Journal of Applied Physics, 2005
    Co-Authors: Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, Fred E Schubert, A J Fischer, Mary H Crawford, K H A Bogart, Andrew A Allerman
    Abstract:

    The junction temperature and thermal resistance of AlGaN and GaInN ultraviolet (UV) light-emitting diodes (LEDs) emitting at 295 and 375 nm, respectively, are measured using the temperature coefficient of diode-Forward Voltage. An analysis of the experimental method reveals that the diode-Forward Voltage has a high accuracy of ±3°C. A comprehensive theoretical model for the dependence of diode-Forward Voltage (Vf) on junction temperature (Tj) is developed taking into account the temperature dependence of the energy gap and the temperature coefficient of diode resistance. The difference between the junction Voltage temperature coefficient (dVj/dT) and the Forward Voltage temperature coefficient (dVf/dT) is shown to be caused by diode series resistance. The data indicate that the n-type neutral regions are the dominant resistive element in deep-UV devices. A linear relationship between junction temperature and current is found. Junction temperature is also measured by the emission-peak-shift method. The high-energy slope of the spectrum is explored in the measurement of carrier temperature.

  • junction temperature in light emitting diodes assessed by different methods
    Light-emitting diodes : research manufacturing and application. Conference, 2005
    Co-Authors: Sameer Chhajed, Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, Fred E Schubert
    Abstract:

    The junction temperature of red (AlGaInP), green (GaInN), blue (GaInN), and ultraviolet (GaInN) light-emitting diodes (LEDs) is measured using the temperature coefficients of the diode Forward Voltage and of the emission-peak energy. The junction temperature increases linearly with DC current as the current is increased from 10 mA to 100 mA. For comparison, the emission-peak-shift method is also used to measure the junction temperature. The emission-peak-shift method is in good agreement with the Forward-Voltage method. The carrier temperature is measured by the high-energy-slope method, which is found to be much higher than the lattice temperature at the junction. Analysis of the experimental methods reveals that the Forward-Voltage method is the most sensitive and its accuracy is estimated to be ± 3°C. The peak position of the spectra is influenced by alloy broadening, polarization, and quantum confined Stark effect thereby limiting the accuracy of the emission-peak-shift method to ±15°C. A detailed analysis of the temperature dependence of a tri-chromatic white LED source (consisting of three types of LEDs) is performed. The analysis reveals that the chromaticity point shifts towards the blue, the color-rendering index (CRI) decreases, the color temperature increases, and the luminous efficacy decreases as the junction temperature increases. A high CRI > 80 can be maintained, by adjusting the LED power so that the chromaticity point is conserved.

  • junction and carrier temperature measurements in deep ultraviolet light emitting diodes using three different methods
    Applied Physics Letters, 2005
    Co-Authors: Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, A J Fischer, Mary H Crawford, K H A Bogart, E F Schubert, Andrew A Allerman
    Abstract:

    The junction temperature of AlGaN ultraviolet light-emitting diodes emitting at 295nm is measured by using the temperature coefficients of the diode Forward Voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-Forward Voltage is the most accurate (±3°C). A theoretical model for the dependence of the diode Forward Voltage (Vf) on junction temperature (Tj) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6K∕W is obtained with the device mounted with thermal paste on a heat sink.

  • junction temperature measurement in gan ultraviolet light emitting diodes using diode Forward Voltage method
    Applied Physics Letters, 2004
    Co-Authors: Y Xi, E F Schubert
    Abstract:

    A theoretical model for the dependence of the diode Forward Voltage (Vf) on junction temperature (Tj) is developed. An expression for dVf∕dT is derived that takes into account all relevant contributions to the temperature dependence of the Forward Voltage including the intrinsic carrier concentration, the band-gap energy, and the effective density of states. Experimental results on the junction temperature of GaN ultraviolet light-emitting diodes are presented. Excellent agreement between the theoretical and experimental temperature coefficient of the Forward Voltage (dVf∕dT) is found. A linear relation between the junction temperature and the Forward Voltage is found.

E F Schubert - One of the best experts on this subject based on the ideXlab platform.

  • junction and carrier temperature measurements in deep ultraviolet light emitting diodes using three different methods
    Applied Physics Letters, 2005
    Co-Authors: Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, A J Fischer, Mary H Crawford, K H A Bogart, E F Schubert, Andrew A Allerman
    Abstract:

    The junction temperature of AlGaN ultraviolet light-emitting diodes emitting at 295nm is measured by using the temperature coefficients of the diode Forward Voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-Forward Voltage is the most accurate (±3°C). A theoretical model for the dependence of the diode Forward Voltage (Vf) on junction temperature (Tj) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6K∕W is obtained with the device mounted with thermal paste on a heat sink.

  • junction temperature measurement in gan ultraviolet light emitting diodes using diode Forward Voltage method
    Applied Physics Letters, 2004
    Co-Authors: Y Xi, E F Schubert
    Abstract:

    A theoretical model for the dependence of the diode Forward Voltage (Vf) on junction temperature (Tj) is developed. An expression for dVf∕dT is derived that takes into account all relevant contributions to the temperature dependence of the Forward Voltage including the intrinsic carrier concentration, the band-gap energy, and the effective density of states. Experimental results on the junction temperature of GaN ultraviolet light-emitting diodes are presented. Excellent agreement between the theoretical and experimental temperature coefficient of the Forward Voltage (dVf∕dT) is found. A linear relation between the junction temperature and the Forward Voltage is found.

Siddharth Rajan - One of the best experts on this subject based on the ideXlab platform.

  • low resistance gan tunnel homojunctions with 150 ka cm2 current and repeatable negative differential resistance
    Applied Physics Letters, 2016
    Co-Authors: Fatih Akyol, Sriram Krishnamoorthy, Yuewei Zhang, Jared M Johnson, Jinwoo Hwang, Siddharth Rajan
    Abstract:

    We report GaN n++/p++ interband tunnel junctions with repeatable negative differential resistance and low resistance. Reverse and Forward tunneling current densities were observed to increase as Si and Mg doping concentrations were increased. Hysteresis-free, bidirectional negative differential resistance was observed at room temperature from these junctions at a Forward Voltage ∼1.6 V. Thermionic PN junctions with GaN homojunction tunnel contact to the p-layer exhibited Forward current density of 150 kA/cm2 at 7.6 V, with a low series device resistance of 1 × 10−5 Ω cm2.

  • low resistance gan tunnel homojunctions with 150 ka cm 2 current and repeatable negative differential resistance
    arXiv: Materials Science, 2016
    Co-Authors: Fatih Akyol, Sriram Krishnamoorthy, Yuewei Zhang, Jared M Johnson, Jinwoo Hwang, Siddharth Rajan
    Abstract:

    We report GaN n++/p++ interband tunnel junctions with repeatable negative differential resistance and low resistance. Reverse and Forward tunneling current densities were observed to increase as Si and Mg doping concentrations were increased. Hysteresis-free, bidirectional negative differential resistance was observed at room temperature from these junctions at a Forward Voltage of ~1.6-2 V. Thermionic PN junctions with tunnel contact to the p-layer exhibited Forward current density of 150 kA/cm^2 at 7.6 V, with a low series device resistance of 1 x 10^-5 this http URL^2.

Amos G Winter - One of the best experts on this subject based on the ideXlab platform.

  • using feed Forward Voltage control to increase the ion removal rate during batch electrodialysis desalination of brackish water
    Desalination, 2019
    Co-Authors: Sahil R Shah, Sandra L Walter, Amos G Winter
    Abstract:

    Abstract Batch electrodialysis (ED) desalination, which relies on diluate recirculation to produce a desired product, is often conducted at constant Voltage. Here we show that constant-Voltage operation under-utilizes membrane area because the applied current is much lower than the limiting current early in a batch cycle. Time-variant Voltage-control, targeted at raising the average ratio of applied to limiting current during a batch cycle, can therefore increase the rate of ion-transfer achievable using a fixed membrane area. We designed a feed-Forward Voltage controller, which provided within −15 to +20% of the desired current, and used it to raise the production rate by up to 37% ± 2%, relative to constant-Voltage operation, without exceeding the limiting current density. Furthermore, an analytical prediction of the batch completion times was derived and validated under varying feeds (1500, 2000, and 3000 mg/L), products (200, 300, and 500 mg/L), and flow velocities (4.3, 6.4, and 8.5 cm/s). Supported by experiments, the predictive model indicates that time-variant Voltage-control can provide the greatest increase in production rate at high feed-to-product concentration ratios and low flow velocities. This work will assist designers and operators seeking to size, evaluate, and maximize the production performance of new and existing batch ED processes.

  • using feed Forward Voltage control to increase the ion removal rate during batch electrodialysis desalination of brackish water
    Desalination, 2019
    Co-Authors: Sahil Shah, Sandra L Walter, Amos G Winter
    Abstract:

    Abstract Batch electrodialysis (ED) desalination, which relies on diluate recirculation to produce a desired product, is often conducted at constant Voltage. Here we show that constant-Voltage operation under-utilizes membrane area because the applied current is much lower than the limiting current early in a batch cycle. Time-variant Voltage-control, targeted at raising the average ratio of applied to limiting current during a batch cycle, can therefore increase the rate of ion-transfer achievable using a fixed membrane area. We designed a feed-Forward Voltage controller, which provided within −15 to +20% of the desired current, and used it to raise the production rate by up to 37% ± 2%, relative to constant-Voltage operation, without exceeding the limiting current density. Furthermore, an analytical prediction of the batch completion times was derived and validated under varying feeds (1500, 2000, and 3000 mg/L), products (200, 300, and 500 mg/L), and flow velocities (4.3, 6.4, and 8.5 cm/s). Supported by experiments, the predictive model indicates that time-variant Voltage-control can provide the greatest increase in production rate at high feed-to-product concentration ratios and low flow velocities. This work will assist designers and operators seeking to size, evaluate, and maximize the production performance of new and existing batch ED processes.

Andrew A Allerman - One of the best experts on this subject based on the ideXlab platform.

  • junction temperature in ultraviolet light emitting diodes
    Japanese Journal of Applied Physics, 2005
    Co-Authors: Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, Fred E Schubert, A J Fischer, Mary H Crawford, K H A Bogart, Andrew A Allerman
    Abstract:

    The junction temperature and thermal resistance of AlGaN and GaInN ultraviolet (UV) light-emitting diodes (LEDs) emitting at 295 and 375 nm, respectively, are measured using the temperature coefficient of diode-Forward Voltage. An analysis of the experimental method reveals that the diode-Forward Voltage has a high accuracy of ±3°C. A comprehensive theoretical model for the dependence of diode-Forward Voltage (Vf) on junction temperature (Tj) is developed taking into account the temperature dependence of the energy gap and the temperature coefficient of diode resistance. The difference between the junction Voltage temperature coefficient (dVj/dT) and the Forward Voltage temperature coefficient (dVf/dT) is shown to be caused by diode series resistance. The data indicate that the n-type neutral regions are the dominant resistive element in deep-UV devices. A linear relationship between junction temperature and current is found. Junction temperature is also measured by the emission-peak-shift method. The high-energy slope of the spectrum is explored in the measurement of carrier temperature.

  • junction and carrier temperature measurements in deep ultraviolet light emitting diodes using three different methods
    Applied Physics Letters, 2005
    Co-Authors: Y Xi, Thomas Gessmann, J Q Xi, Jay M Shah, A J Fischer, Mary H Crawford, K H A Bogart, E F Schubert, Andrew A Allerman
    Abstract:

    The junction temperature of AlGaN ultraviolet light-emitting diodes emitting at 295nm is measured by using the temperature coefficients of the diode Forward Voltage and emission peak energy. The high-energy slope of the spectrum is explored to measure the carrier temperature. A linear relation between junction temperature and current is found. Analysis of the experimental methods reveals that the diode-Forward Voltage is the most accurate (±3°C). A theoretical model for the dependence of the diode Forward Voltage (Vf) on junction temperature (Tj) is developed that takes into account the temperature dependence of the energy gap. A thermal resistance of 87.6K∕W is obtained with the device mounted with thermal paste on a heat sink.