Electrochemical potentiostatic activation for improvement of internal quantum efficiency of 385-nm ultraviolet light-emitting diodes

Enhanced Performance of GaN-based Ultraviolet Light Emitting Diodes by Photon Recycling Using Graphene Quantum Dots

“…To further increase the optical output power, it is essential to overcome several drawbacks in the GaN-based UV LEDs including low material quality in AlGaN layer, incomplete current spreading, high optical absorption in the p-GaN clad/contact layers, and high current-induced degradation. Several strategies have been proposed to improve the light output of III-nitride based UV LEDs 6 – 8 . For example, novel geometrical designs such as the quantum-dot and photonic-crystal structures have been suggested to confine the carriers or photons in nanostructures and enhance the light extraction efficiency (LEE) in UV LEDs 6 , 7 .…”

“…For example, novel geometrical designs such as the quantum-dot and photonic-crystal structures have been suggested to confine the carriers or photons in nanostructures and enhance the light extraction efficiency (LEE) in UV LEDs 6 , 7 . In addition, an electrochemical potentiostatic activation method has led to the activation of p-type materials, which is beneficial for improvement of the internal quantum efficiency (IQE) 8 . The transparent and current spreading electrode materials of GaN-based LEDs have also been investigated 4 , 9 , 10 .…”

Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

“…In an earlier report, we demonstrated that forward I-V (current-voltage) characteristics exhibited almost the same behavior. 27 In a detailed analysis in the region of 1 V-2 V, the current levels were decreased as the EPA voltage was increased, as shown in Figure 7. At 1.5 V, the current value of LED chips processed by EPA at 7 V demonstrated more than one order lower current compared with those activated by conventional annealing.…”

“…This is clearly observed in Figure 3 that the optical output power was significantly improved after the EPA process at 3 V. As a result, the hydrogen concentration was reduced by about 32%, showing a light output enhancement of $20% from 72 mW to 86 mW at 50 mA, as reported before. 27 However, it is striking that the optical output of LEDs EPA processed at 5 V demonstrate just $8% improvement to 78 mW at 50 mA. This is very difficult to predict with certainty, because the hydrogen concentration is decreased more after the EPA process at 5 V. Moreover, after the EPA process at 7 V, the LED chips showed deteriorated device performance compared with LED chips activated by conventional annealing.…”

“…26,27 This electrochemical potentiostatic activation (EPA) method is practical for enhancing the light output performance of 385-nm LEDs. In this paper, we investigate the EPA process in detail in regard to process parameters and the performance of the GaN-based a)…”