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Effect of Interface State Density of the AlGaN Electron Blocking Layer/GaN Barrier Layer in InGaN Blue Light-Emitting Diodes
摘要： Herein, two kinds of blue InGaN light-emitting diodes (LEDs) were compared in order to understand the effect of the strain originating from two different sapphire substrates. One of the LED types was grown on a patterned sapphire substrate (PSS), and the other was grown on a conventional sapphire substrate (CSS). The internal strains biased on InGaN quantum wells were compared by studying the time-resolved photoluminescence and the electroreflectance. Through analysis of the dynamic capacitance dispersion measurements, the relation between the trap states and trap density of the AlGaN electron blocking layer/GaN barrier interface above the InGaN quantum wells can be understood in great detail. The trapped charges of the CSSs have faster response times than those of the PSSs; this is attributed to the stronger piezo-field, which induces the AlGaN EBL/GaN barrier interface trap states to be effectively located at shallower levels from the conduction band.
关键词： Strain,Patterned sapphire substrate,InGaN quantum wells
更新于2025-09-23 15:19:57
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Light Extraction Efficiency Optimization of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
摘要： Using finite-difference time-domain method, the light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) is investigated. Simulation results show that compared to flat sapphire substrate, the nano-patterned sapphire substrate (NPSS) expands the extraction angles of top surface and sidewalls. As a result, the LEE of transverse-magnetic (TM) polarized light is improved significantly. Roughening on the backside of n-AlGaN surface significantly enhances the LEE of top surface of thin-film flip-chip DUV LEDs. However, the LEE of sidewalls of thin-film flip-chip DUV LEDs is greatly weakened. For bare DUV LED, the LEE of flip-chip LED on NPSS is estimated to be about 15%, which is around 50% higher than that of thin-film flip-chip DUV LED with roughening on the backside of n-AlGaN surface.
关键词： AlGaN,nano-patterned sapphire substrate,light-emitting diodes,deep-ultraviolet,light extraction efficiency
更新于2025-09-23 15:19:57
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Suppressing the Initial Growth of Sidewall GaN by Modifying Micron-Sized Patterned Sapphire Substrate with H3PO4-Based Etchant
摘要： Micron-sized patterned sapphire substrates (PSS) are used to improve the performance of GaN-based light-emitting diodes (LEDs). However, the growth of GaN is initiated not only from the bottom c-plane but also from the sidewall of the micron-sized patterns. Therefore, the coalescence of these GaN crystals creates irregular voids. In this study, two kinds of nucleation layers (NL)—ex-situ AlN NL and in-situ GaN NL—were used, and the growth of sidewall GaN was successfully suppressed in both systems by modifying the micron-sized PSS surface.
关键词： growth of GaN,micron-sized patterned sapphire substrate,sidewall GaN
更新于2025-09-09 09:28:46