We have integrated the surface photonic crystal (PhC) on GaN-based blue light-emitting diodes (LEDs) for the first time in order to enhance the extraction efficiency of the LEDs. With the finite-difference time-domain method, we have calculated 3.6-fold enhancement in light output. The theoretical calculations have revealed that the optimum pitch of the PhC is much longer than the emission wavelength when the distance between the PhC and the active layer of LEDs is short. This design enables PhC formation on chemically stable GaN surfaces. In addition, an indium tin oxide (ITO)-based transparent electrode is formed directly on the surface of PhC to realize light emission from the whole area of the LED. The fabricated PhCs have increased the light output of blue LEDs by 1.5 times compared with the LEDs without PhC. We have demonstrated that PhC will realize highly efficient solid-state lighting with GaN-based LEDs.

This paper reports an extensive analysis of the properties of the deep level responsible for the degradation of InGaN-based laser diodes. The analysis is based on combined optical measurements and Deep-Level Transient Spectroscopy (DLTS) investigation. Results indicate that stress induces a significant increase in threshold current of the devices, which is strongly correlated to the increase in the concentration of a deep level (DL) detected by DLTS. The DL involved in the degradation process is located 0.35–0.45 eV below the conduction band. 2D simulation indicates that degradation occurs within the quantum-well region

In this paper we present a detailed analysis of the degradation of InGaN-based laser diodes carried out by means of electrical and optical techniques. The study is based on the comparison between the degradation kinetics of laser diodes and light-emitting diode LED-like samples, i.e., devices with the same epitaxial structure as the lasers, but with no ridge and facets. Results described in the following indicate that degradation of lasers and LED-like samples is due to the same mechanism, possibly involving the generation of point defects within the active region of the devices. Furthermore, since degradation occurs both in lasers and in LED-like samples i.e., structures with no current confinement, results suggest that degradation of lasers is not correlated with the geometry of the devices, nor to worsening of current confinement under the ridge

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