低電流密度下極化效應對微型LED內部量子效率影響之研究

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Title:	低電流密度下極化效應對微型LED內部量子效率影響之研究
Authors:	劉亞綸;Liu, Ya-Lun
Contributors:	光機電工程研究所
Keywords:	半極性晶向;發光二極體;內部量子效率;微發光二極體;單量子井;低電流密度;semi-polar orientation;LEDs;internal quantum efficiency;micro-LEDs;single quantum well;low current density
Date:	2023-07-18
Issue Date:	2023-10-04 14:51:41 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究探討半極性晶向之單量子井(single quantum well, SQW) 藍光微發光二極體(µ-LED)於低電流密度下之光電特性。藉由模擬分析，探討8種晶向與不同QW厚度對內部量子效率(internal quantum efficiency, IQE)與正向電壓之影響。模擬結果發現pn-接面之內建電場與反向極化導致之電場在低電流密度下對IQE與正向電壓有顯著的影響。由能帶圖的分析顯示非極性發光二極體因內建電場導致的能帶傾斜而並非擁有最高的IQE與最大允許厚度。另外，反向極化會增加與內建電場同向之能帶傾斜，故較於接近非極性之(11-22)微發光二極體於較大QW厚度有較差的IQE。但反向極化也會減少電洞能障高度，故可在同電流密度下有更低的正向電壓。最後發現低電流密度下，於本文討論之8種晶向中，弱正向極化(10-12)微發光二極體有最高IQE與最大允許厚度，這源於弱正向極化之電場與內建電場間的平衡，使其擁有最平整的能帶。;This study investigates the optoelectronic properties of blue micro-light-emitting diodes (µ-LED) based on the semipolar single quantum well (SQW) at low current density. Through simulation analysis, the influences of eight crystal orientations and different QW thicknesses on internal quantum efficiency (IQE) and forward voltage are investigated. The simulation results show that, at low current density, the built-in electric field of the p–n junction and the electric field caused by reversed polarization have a significant effect on the IQE and forward voltage. Analysis of the energy band diagram shows that non-polar LEDs do not exhibit the highest IQE and maximum allowed thickness, owing to the energy band tilt caused by the built-in electric field. Additionally, reversed polarization increases band tilt in the same direction as the built-in electric field, resulting in poorer IQE compared to non-polar LEDs. However, reversed polarization also reduces hole barrier height, resulting in lower forward voltage at the same current density. Finally, it is found that weakly positive-polarized (10-12) LEDs have the highest IQE and maximum allowed thickness at low current density, which is due to the flat energy band with reduced band tilt caused by weakly positive polarization.
Appears in Collections:	[Graduate Institute of opto-Mechatronics] Electronic Thesis & Dissertation

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