Abstract-In this paper, InGaN/GaN nanorod LEDs with various sizes are fabricated using self-assembled Ni nanomasks and inductively coupled plasma-reactive ion etching. Photoluminescence (PL) characteristics exhibit size-dependent, wavelength blue shifts of the emission spectra from the nanorod LEDs. Numerical analyses using a valence force field model and a self-consistent Poisson, Schrödinger, and drift-diffusion solver quantitatively describe the correlation between the wavelength blue shifts and the strain relaxation of multiple quantum wells embedded in nanorods with different averaged sizes. Time-resolved PL studies confirm that the array with a smaller size exhibits a shorter carrier lifetime at low temperature, giving rise to a stronger PL intensity. However, the PL intensity deteriorates at room temperature, compared to that of a larger size, possibly due to an increased number of surface states, which decreases the nonradiative lifetime, and hence reduces the internal quantum efficiency.

Femtosecond pulses at wavelengths ranging from 750to900nm (1.38–1.65eV) were used in the excitation and probing of ultrafast carrier dynamics in InN epitaxial films. Experimental results show that the hot electron relaxation rate increases with increasing electron energy, which is measured as E0.53. This observation agrees with the prediction of electron-electron scattering relaxation mechanism. In addition, the electron-hole recombination rates are independent of the electron energy and have values of ∼7×109Hz. We attribute this result to the Auger recombination in InN being insensitive to temperature.

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Ultrafast hot carrier dynamics in Indium nitride (InN) epitaxial films were investigated by femtosecond time-resolved pump-probe reflection measurements. Carrier density and carrier energy dependence of the hot carrier dynamics in InN were studied by varying the pump laser power and wavelength, respectively. Experimental results showed that the hot carrier relaxation can be fitted by a biexponential relaxation process. The fast relaxation rate increased with increasing carrier density (N), which was measured as N 0.5 . The fast relaxation rate also increased with increasing carrier energy (E), which was measured as E 0.53 . These observations revealed that electron-electron scattering plays an important role in the fast relaxation process. The slow relaxation process was found to be dominated by Auger scattering and the slow relaxation rate was independent of the carrier energy. The defect-related trapping time in InN was estimated to be ~515 ps.