No abstract

Reverse-bias operations for a light-emitting diode can quickly screen the weakness of the device. Electromigration around the electrode on the lateral and vertical directions can be observed by optical microscope images, scanning electron microscope images and energy dispersive spectroscopy. The failure process caused by the electromigration can be revealed by the changes of forward-bias and reverse-bias electroluminescence images and the emergence of the reverse-bias EL may be attributed to the diffusion of gold. Furthermore, the increase of the leakage current may supress the forward-bias band to band recombination current especially near the metal contact.Introduction: With the development of the GaN-based light-emitting diodes (LEDs), reliability issues have become unavoidable because of the innate defects and the imperfect contacts of the GaN materials. High reverse-bias voltage stress has been proposed to reveal the weak structures because a high electric field can pinpoint the fabrication problems [1,2]. In this reported research, we investigated the LED degradation trend under reverse-bias operations in water vapour [3]. Electromigration around the electrode both on the lateral and the vertical directions can be revealed by microscope optical images, scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDX) [4]. The enlargement of the reverse-bias EL and the waning of the forward-bias EL may be attributed to the diffusion of gold.

No abstract

In this study, we present and experimentally demonstrate an erbium-doped fiber (EDF) quad-fiber-ring (QFR) laser with selectable and flat single-longitudinal-mode (SLM) wavelength output. The designed QFR scheme not only can suppress dense multi-mode oscillation, but also can broaden and flatten the output wavelength covering C- and part of L-bands over a bandwidth from 1519.0 to 1579.0 nm when using a C-band EDF as gain medium. Additionally, the output power, optical signal to signal ratio (OSNR), linewidth, stability and tunability of the proposed EDF laser are also discussed.