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www.omdl.tw Temperature dependence of performance of InGaN/GaN MQW LEDs YC Chiang STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Outline www.omdl.tw • Motive • Temperature dependence Different MQW Structures Different Indium Compositions • Results and Discussion • Conclusions • Reference STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 2 Motive www.omdl.tw • The impact of temperature on the LED for a great • Hot-Cold effect STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 3 www.omdl.tw • Experimental • Results and Discussion • Conclusions STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 4 p-AlGaN重要性 www.omdl.tw • Add a layer of LED are now p-AlGaN electron blocking layer to block electron overflow. • The disadvantage is that Vf rise will increase the resistance STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 5 Experimental www.omdl.tw Chip size：300 x 300 μm2 p-contact Without p-AlGaN：LED A With p-AlGaN：LED B ITO p-GaN p-AlGaN five pairs In0.25Ga0.75N/GaN n-contact n-GaN n-GaN un-doped GaN 30nm buffer layer Sapphire STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 6 Results and Discussion www.omdl.tw Why? 可增加電子侷限犧牲的是Vf上升 Figure 1. I-V characteristics of the LEDs with and without a p-AlGaN cladding layer above InGaN/GaN MQW structure. STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 7 Results and Discussion www.omdl.tw 避開AlGaN會影響波長的現象 微觀去看其實波長飄蠻多的 Figure 2. (a) Electroluminescence spectra for two LEDs at room temperature. (b) Variation of dominant peak wavelength of two LEDs as a function of the temperature. STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 8 Al 含量對極化的影響 STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY www.omdl.tw 9 Results and Discussion www.omdl.tw 可增加電子侷限效應 Figure 3. Output powers of two unpackaged LEDs as a function of injection current at room temperature. STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 10 Results and Discussion 因為多了一層電子阻擋層使得在溫度上升時有良好的店子侷限能力 www.omdl.tw Figure 4. Normalized output intensities and fitted lines of two LEDs as a function of the temperature at a constant current of 20 mA. STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 11 Conclusions www.omdl.tw • The output power for an LED with a p-AlGaN electron blocking layer above the MQWs dropped more slowly than that of LED without this layer due to a reduction in overflowing electrons from quantum well active region. • Increased radiation recombination in the active region due to better carrier confinement for the p-AlGaN cladding layer. STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 12