Internal quantum efficiency (IQE) of a blue highbrightness InGaN/GaN LED was evaluated from the external quantum efficiency measured as a function of current at various temperatures ranged between 13 K and 440 K. Processing the data with a novel evaluation procedure based on the ABC-model, we have determined the temperature dependent IQE of the LED structure and light extraction efficiency of the LED chip. Separate evaluation of these parameters is helpful for further optimization of the heterostructure and chip designs. The data obtained enable making a guess on the temperature dependence of the radiative and Auger recombination coefficients, which may be important for identification of dominant mechanisms responsible for the efficiency droop in III-nitride LEDs. Thermal degradation of the LED performance in terms of the emission efficiency is also considered.

Based on numerical simulation and comparison with measured current characteristics, we show that the current in InGaN/GaN single-quantum-well light-emitting diodes at low forward bias can be accurately described by a standard trap-assisted tunneling model. The qualitative and quantitative differences in the current characteristics of devices with different emission wavelengths are demonstrated to be correlated in a physically consistent way with the tunneling model parameters

Determination of the complex dielectric function and the critical-point energies of (Al x Ga 1Ϫx) 0.51 In 0.49 P, over the full range of composition x and for photon energies E from 0.75 to 5 eV is reported from variable angle of incidence spectroscopic ellipsometry. Native-oxide effects on the (Al x Ga 1Ϫx) 0.51 In 0.49 P optical functions are removed numerically. The highly disordered state of the metalorganic vapor-phase epitaxy grown samples is analyzed by transmission electron microscopy. Optical anisotropy investigations revealed that the order-induced optical birefringence is negligible throughout. The augmentation of A. D. Rakić and M. L. Majewski ͓J. Appl. Phys. 80, 5909 ͑1996͔͒ to Adachi's critical-point model, i.e., consideration of Gaussian-like broadening function instead of Lorentzian broadening, is used for calculation of the isotropic (Al x Ga 1Ϫx) 0.51 In 0.49 P dielectric function. The optical functions spectra consistently match the experimental data, whereas previously reported model dielectric functions fail to reproduce the correct absorption behavior of the quaternary, especially near the fundamental band-to-band transition. The results are compared to those presented previously, and influence of spontaneous chemical ordering is discussed.

We suggest a novel technique for the evaluation of the recombination coefficients corresponding to Shockley–Read–Hall, radiative, and Auger recombination that occur in InGaN/GaN-based light-emitting diodes (LEDs). This technique combines the measurement of the LED efficiency as a function of LED drive current with a small-signal time-resolved photoluminescence measurement of the differential carrier life time (DLT). Using the relationships between the efficiency and DLT following from the empirical ABC-model, one can evaluate all three recombination coefficients. The suggested technique is applied to a number of single- and multiple-quantum well LEDs to gain a deeper insight into the mechanisms ultimately limiting their efficiency