Search

Investigates a band gap shrinkage in both lattice-matched and compressive strained gallium (Ga)-indium (In)-arsenic (As)/GaInAs-phosphorus (P)/InP multi-quantum well lasers. Reason for the difficulty in quantifying the pure band gap shrinkage from the measured broadening; Determination of the broadening of the long wavelength side in the spectrum; Use of Lorentzian function.

We demonstrate a modeling method based on the three-dimensional electrical and thermal circuit analysis to extract current, voltage and temperature distributions of light-emitting diodes (LEDs). In our model, the electrical circuit analysis is performed first to extract the current and voltage distributions in the LED. Utilizing the result obtained from the electrical circuit analysis as distributed heat sources, the thermal circuit is set up by using the duality between Fourier's law and Ohm's law. From the analysis of the thermal circuit, the temperature distribution at each epitaxial film is successfully obtained. Comparisons of experimental and simulation results are made by employing an InGaN/GaN multiple-quantum-well blue LED. Validity of the electrical circuit analysis is confirmed by comparing the light distribution at the surface. Since the temperature distribution at each epitaxial film cannot be obtained experimentally, the apparent temperature distribution is compared at the surface of the LED chip. Also, experimentally obtained average junction temperature is compared with the value calculated from the modeling, yielding a very good agreement. The analysis method based on the circuit modeling has an advantage of taking distributed heat sources as inputs, which is essential for high-power devices with significant self-heating. [ABSTRACT FROM AUTHOR]

An electrode pattern design methodology that improves the current uniformity in mesa-structured GaN/InGaN blue light-emitting diodes (LEDs) is investigated. Comparisons between an LED with a new electrode pattern adopting the proposed methodology and an LED with a commercially used electrode are made in view of both current and luminance distributions. Simulations as well as experimental results show that the proposed simple design methodology is very effective to spread current more uniformly in the active layer. [ABSTRACT FROM AUTHOR]

The authors analyzed radiative efficiency of InGaN laser diodes (LDs) emitting at 405 nm. Based on semiconductor rate equations, the radiative efficiency is unambiguously determined by the analysis of electroluminescence characteristics. The radiative efficiency exceeds 70% even far below threshold of ∼3 mA at a high temperature of 80 °C. This highly radiative characteristic is attributed to reduced contribution of nonradiative recombination in LDs with low-dislocation-density active material. It is also found that the radiative efficiency is almost independent of threshold current, indicating that nonradiative recombination is not a major factor which determines lasing threshold in 405 nm emitting InGaN LDs having low dislocation density. [ABSTRACT FROM AUTHOR]