具微米三角柱結構氮化鎵發光二極體之研製

Abstract

本研究論文在探討氮化銦鎵�氮化鎵發光二極體之製作與特性量測，第一部分重點在於光致電化學氧化法成長之氧化鎵薄膜對於發光二極體之表面鈍化效果與表面出光增益之影響。 在光激螢光強度的量測中，我們觀察到氧化鎵薄膜具有表面鈍化效應與抗反射膜作用，使得光激螢光頻譜上具有光學增益的效果；在氮化鎵頻譜範圍中心波長365nm部分的訊號強度約有60％的增強，而在量子井主動層頻譜範圍中心波長450nm約有80％訊號強度的提升。 在電壓－電流特性量測中，具有氧化鎵薄膜保護層之氮化銦鎵�氮化鎵發光二極體元件並未有特性劣化之現象。由電激螢光強度量測的結果顯示，與未成長氧化膜之元件相較，在中心波長處約有40％的增強，且在10伏特的逆向偏壓下，漏電流約有30％之改善。且在電激發光輻射場型的量測中，可觀察到成長氧化膜之元件在各方向上的出光強度有所增加，尤其在側向角度上有較高的增強比例。 第二部分，我們利用平坦化製程，並結合前述氧化層鈍化技術，成功完成具微米三角柱結構發光二極體製程技術之開發。在電性量測中，具氧化鈍化層之微米三角柱發光二極體元件漏電流，相較於未氧化之元件降低約兩個數量級。而在電激發光輻射場型的量測中，可觀察到微米三角柱結構發光二極體在側向角度之出光上，與一般平面型發光二極體相比，具有較高比例的出光強度。

The fabrication and characterization of InGaN/GaN light-emitting diode are investigated in this thesis. First, we discuss the characteristics of native gallium oxide layer grown by photoelectrochemical (PEC) oxidation. The photoluminescence (PL) enhancement of PEC passivated GaN and quantum well active layer are ~60％ and ~80％, respectively. These significant increases of PL intensity can be ascribed to the passivation of dangling bonds and the anti-reflection effect of native gallium oxide layer. Then, the testing light-emitting diode (LED) with conventional planar structure was examined by Agilent 4155C semiconductor analyzer. The characteristic I-V curve of PEC passivated LED reveals a typical forward voltage 4.3V at 20mA with 40％ increase in electroluminescence intensity and 30％ reduction in leakage current at reverse bias 10V. Moreover, the radiation pattern shows that light intensity of PEC passivated LED is higher than that of non-passivated LED in all direction, especially in oblique angle. Finally, we successfully combine the planarization and PEC passivation technique to fabricate micron-scale triangular structure light-emitting diode. Leakage current of this device with oxide passivation layer is reduced about 2 orders compared to triangular structure device without oxide layer. Moreover, the radiation pattern shows that the percentage of light intensity in oblique angle of micron-scale triangular LED is higher than that of typical planar LED.