Degradation of blue LEDs related to structural disorder

Abstract

The degradation of blue light emitting diodes (LEDs) with different structural disorder based on MQW InGaN/GaN grown by MOCVD on sapphire has been investigated. New approach to analyze the degradation has been used. It takes into account the structural disorder determined by the extended defect system relaxation and related with poor coalescence of the mosaic structure domains. The results obtained leads to assumption that the migration and segregations of Ga on domain dislocation boundaries of the mosaic structure and the change of energy activation of Mg related centers are important reasons of degradation for all types of LEDs The fastest degradation for poor ordered LEDs was observed.

Peculiarities of defect generation under injection current in LEDs based on group‐III nitride3N nanostructures

“…Note that commercial blue LEDs fabricated by various manufacturers may differ by the value of shunt conductivity only before the aging. It was found earlier that the value of shunt conductivity or leakage current at U < 2 V can be used to characterize integral properties of EDS in InGaN/GaN LEDs [5,10]. The lower the leakage current values, the smaller the nano-structural disorder (the weaker EDS) is in the LED material [5,10].…”

“…The role of point defects and an extended defect system (EDS) as well as defect generation in p+ and n+ region of the LED structure in the degradation is also under discussion. A local overheating observed in A 3 N LEDs during aging [1,4,5] demonstrates that the defect generation process in A 3 N materials, which is accompanied by local multiplication of dislocations and creation of a dislocation net, is unlike the one in traditional A 3 B 5 materials. The peculiarities of the defect formation under current injection are thought to be related to the complicated defect structure of A 3 N LED materials having a fractal nature, which is a manifestation of both the EDS piercing of the active region and local regions of alloy randomness.…”

“…Migration of Alatoms (for UV LEDs) and of Ga-and In-atoms (for blue LEDs) have been also considered [1,3,5]. However a generally accepted mechanism or cooperation of mechanisms capable to describe all peculiarities of EQE degradation and catastrophic failure of LEDs is not yet present.…”

Study of mechanisms responsible for the efficiency degradation of the III-nitrides light emitting diodes

“…Этот процесс вызывает образование дефектов по Френкелю и их миграцию. Подтверждением возможности развития этого процесса являются экспериментальные данные, полученные как в этой ра-боте, так и другими исследователями на InGaN/GaN светодиодах, по выявлению миграции индия вдоль прорастающих дислокаций методами просвечивающей микроскопии [11] и по выделению индия и галлия в локальных областях на поверхности светодиодов [12] после финальной стадии старения.…”

“…Эти процессы не наблюдаются в светодиодах на основе нитридов третьей группы [10]. Более того, наблюдается влияние токов утечки, шунтирующих p-n-переход, на распределение электролюминесценции по площади светодиода [6] и появление локальных областей перегрева на финальной стадии деградации [11,12], а также миграция галлия и индия вдоль дислокаций [11] с выделением металлической фазы на поверхности [12]. В связи с этим был сделан вы-вод о диффузии точечных дефектов и примесей вдоль прорастающих дислокаций в активной области светодиодной структуры [10].…”