Engineering Design of High Quality GaN Epitaxy on Silicon Substrate Using Varying GaN/AIGaN Composite Buffer Structures
High quality GaN epitaxy thin films have been desired for the energy-efficient, solid-state semiconductor illuminating devices. Silicon substrates offer high crystal quality, low wafer cost, large wafer size, and potential integration with the well-established silicon processing technologies. However, due to the large mismatch in lattice constants and thermal expansion coefficients, it is still challenging to grow high quality GaN on silicon substrates. In this study, high quality GaN epitaxy has been engineering designed to grow on Si(lll) substrate using varying GaN/AIGaN composite buffer structures by an Axitron 200 metal-organic vapor phase epitaxy deposition system. A thin A1N seed layer of 25 nm was firstly grown at 720 °C. AlGaN layer of different thickness was then grown at 1050°C with subsequent GaN thin film until the total thickness reached 500 nm. The thickness of the subsequent GaN thin film could be increased by reducing the AlGaN thickness in the composite buffer structures. The results have shown that the lower GaN/AIGaN thickness ratio would decrease the dislocation density and provide crack-free, mirror-like upper GaN crystal thin film. On the other hand, the GaN/AIGaN thickness ratio could be designed to be 2-6 to balance the processing cost and the thin film quality for engineering applications. The dislocation density has been about 2× 109 cm-2. In addition, dislocation close loop was observed near the GaN/AIGaN interface. The annihilation mechanism could be depicted by the reduction in dislocation strain energy.
gallium nitride dislocation density silicon substrate buffer layer
Wu G M Tu K N Kuo C C
Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA Ins Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095, USA Institute of Electro-Optical Engineering, Chang Gung University, Kweisan, Taoyuan 333, Taiwan, China
国际会议
西安
英文
57-60
2011-05-11（万方平台首次上网日期，不代表论文的发表时间）