Based on carrier rate equation, a new model is proposed to explain the non-exponential nature of time-resolved photoluminescence (TRPL) decay curves in the polar InGaN/GaN multi-quantum-well structures. From the study of TRPL curves at different temperatures, it is found that both radiative and non-radiative recombination coefficients vary from low temperature to room temperature. The variation of the coefficients is compatible with the carrier density of states distribution as well as the carrier localization process. These results suggest that there is a novel method to calculate the internal quantum efficiency, which is a complement to the traditional one based on temperature dependent photoluminescence measurement.

We have successfully implemented green and red light-emitting diodes (LEDs) based on InGaN/GaN quantum dots (QDs) grown by controlling the process of the growth interruption method using metal organic vapor phase epitaxy (MOVPE). It is found that the three-step growth interruption method and the underlying InGaN/GaN superlattice structure are beneficial for achieving greater indium incorporation in InGaN QDs. As a result, green and red LEDs with electroluminescence (EL) peak energies of 2.28 eV at 20 mA and 1.70 eV at 80 mA, respectively, are demonstrated. The EL emission energy blue shift of the green QD LEDs is 140 meV as injection current increases from 5 to 50 mA, while that of the red LED is 70 meV as injection current increases from 75 to 100 mA.

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InGaN quantum dot (QD) light-emitting diodes (LEDs) were grown by metalorganic vapor phase epitaxy using an interruption method. As the injection current density increased from 2 to 88 A/cm2, the peak electroluminescence (EL) wavelength of the LED remained almost constant at around 527 nm. The negligible blue shift indicates that the quantum-confined Stark effect induced by piezoelectric polarization is suppressed well in InGaN QDs because of strain relaxation. Temperature-dependent EL spectra measurements indicate that the capture of electrons by QDs needs further improvement because of severe electron overflow to the p-type region. In addition, the peak EL wavelength is found to be abnormally longer than the photoluminescence wavelength.