矽基板上氮化物發光二極體之技術發展

Technology Development of Nitride Light-emitting Diode on Silicon Substrate

陳志諺(Chih-Yen Chen)

指導教授 ： 楊志忠

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.11174

摘要

在本論文中，我們實現了生長氮化鋁緩衝層的新穎技術，以降低在矽基板上生長氮化鎵所產生的拉伸應力。藉由溫度漸變的方式生長氮化鋁緩衝層，便可利用氮化鋁緩衝層中的熱應力來抵抗降溫過程在氮化鎵薄膜中所產生的熱應力。我們成功地在(111)面矽基板上生長3.7微米厚的無裂痕氮化鎵薄膜，而拉曼散射分析顯示薄膜中的殘留應力已有效地降低。將這技術應用在生長氮化銦鎵/氮化鎵多重量子井上，可以大幅地降低量子侷限史塔克效應，因而提高量子井的發光強度。我們亦比較了在藍寶石基板及矽基板上所生長的量子井，以分析不同的襯底應力對量子井發光特性的影響，並提出了應力模型來解釋。

因為矽基板會吸收可見光，如何降低吸光所造成的光損耗是提升發光二極體效率的重要議題。為了增強在矽基板上所生長的氮化銦鎵/氮化鎵多重量子井發光二極體的出光效率，我們設計了(110)面的圖案化矽基板，其條狀圖案沿著[1-10]Si || [11-20]AlN 的方向。在條狀圖案化矽基板上所生長的氮化鎵薄膜具有較佳的晶體品質，而散佈在晶圓表面的溝槽可以產生很強的光散射以提升出光。因此，在(110)面條狀圖案化矽基板上所生長的發光二極體，和在(110)及(111)平面矽基板上所生長的發光二極體相較之下，具有較強的光輸出。

此外，我們在Si(111)基板上製作網狀圖案，於其上生長相同的發光二極體結構。並且提出一個應力變化模型來預測，增加溝槽的深度可以降低殘留應力。從電子顯微鏡影像、拉曼散射頻譜及光致發光頻譜的分析結果顯示，較深的溝槽確實可以降低殘留應力。我們也證實了溝槽效應對於應力補償是個很關鍵的限制。

關鍵字

有機金屬化學氣相沉積 ； 矽基氮化鎵 ； 氮化鋁緩衝層 ； 圖案化矽基板

並列摘要

In this dissertation, a novel technique for growing a thick AlN buffer is demonstrated to reduce the tensile stress of GaN grown on silicon substrates. By growing the thick AlN buffer with a temperature-graded method, the thermal stress in AlN buffer can be utilized to counter the thermal stress in GaN layer during the cooling-down process. A 3.7 μm-thick crack-free undoped GaN layer is demonstrated on Si(111) substrate, and the Raman-scattering analysis results show that the residual stress is effectively reduced. By applying this technique to the growth of InGaN/GaN multiple quantum well (MQW), the Quantum-confined Stark effect (QCSE) can be significantly reduced, leading to a higher luminescent intensity. The influences of template strain on the optical properties of QWs are also investigated with the proposed strain model.

Since the silicon substrate is absorptive in the visible-light range, the optical loss is an important issue for the performance of light-emitting diode (LED). In order to enhance the light extraction of InGaN/GaN MQW LEDs grown on Si substrates, we design a stripe-patterned Si(110) substrate with stripes aligned along the [1-10]Si || [11-20]AlN direction. The lateral overgrowth of GaN on stripe-patterned Si(110) substrates results in a superior crystalline quality, and the trenches distributed over the whole wafer produce strong scattering for enhancing light extraction. As a consequence, LEDs grown on the stripe-patterned Si(110) substrate have much higher light output over those of LEDs grown on flat Si(110) and Si(111) substrate.

We also grow the same LED structures on the mesh-patterned Si(111) substrates with different trench depth for comparison. The proposed strain evolution model predicts that the residual stress can be reduced by increasing trench depth. The analysis results from plane-view SEM images, Raman scattering spectra, and PL spectra demonstrate that the residual stress can be reduced by a deep trench. It is proved that the trench effect is a crucial limitation of strain compensation.

並列關鍵字

MOCVD ； GaN on Si ； AlN buffer ； patterned silicon substrate

參考文獻

[1.1] H. Amano M. Iwaya, T. Kashima, M. Katsuragawa, I. Akasaki, J. Han, S. Hearne, J. A. Floro, E. Chason, and J. Figiel, Jpn. J. Appl. Phys. 37, L1540 (1998).

[1.2] K. E. Waldrip, J. Han, J. J. Figiel, H. Zhou, E. Makarona, and A. V. Nurmikko, Appl. Phys. Lett. 78, 3205 (2001).

[1.3] J. Blasing, A. Reiher, A. Dadgar, A. Diez, and A. Krost, Appl. Phys. Lett. 81, 2722 (2002).

[1.4] A. Dadgar, J. Blasing, A. Diez, A. Alam, M. Heuken, and A. Krost, Jpn. J. Appl. Phys. 39, L1183 (2000).

[1.5] A. Reiher, J. Blasing, A. Dadgar, A. Diez, and A. Krost, J. Cryst. Growth 248, 563 (2003).