Selective Area Growth and Characterization of Gallium Nitride Semiconductors on Si by Metal-organicChemical Vapor Deposition

• Main Authors: Guan-Ting Chen, 陳冠廷
• Other Authors: Jen-Inn Chyi
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/56383995549829441953

博士 === 國立中央大學 === 電機工程研究所 === 96 === This dissertation describes selective epitaxial growth techniques of GaN on c-face sapphire and microscale patterned Si substrates. The structural and optical properties of GaN films thus grown, particularly the reduction of dislocation density and residual stress via the selective area epitaxial process and the enhancement of their luminescence properties, are investigated and elucidated. For the selective area epitaxial growth of GaN on c-face sapphire, “pendeoepitaxy” and “facet-controlled epitaxial lateral overgrowth (FACELO)” techniques are employed. Both approaches lead to a significant reduction in dislocation density of the GaN epitaxial layers through a proper arrangement of the lateral enhanced growth mode and vertical enhanced growth mode during the selective area growth. The luminescence properties of InGaN/GaN multiple-quantum-well (MQW) grown on FACELO-GaN are also investigated by cathodoluminescence, and reveal superior efficiency, as compared to the same MQW grown on GaN directly on sapphire. For the selective area growth of GaN on AlGaN/(111)Si, 2 um-thick GaN films without cracks can be achieved by using the substrates with a micropillar array. Transmission electron microscopy (TEM) indicates that dislocation density has been reduced in the lateral growth region, while a large number of dislocations are confined in the heteroepitaxial region. The cathodoluminescence peak intensity of the GaN on AlGaN/(111)Si micropillar array is almost 3 times stronger than that of the GaN on planar AlGaN/(111)Si. It is also found that the residual stress of the GaN grown on AlGaN/(111)Si micropillar array is 0.373 GPa, which is 33.2% lower than that of the GaN grown on planar (111)Si. These results demonstrate the potential of this pillar array template for making low-cost GaN-based devices and free-standing substrates. Semi-polar {1-101}GaN films and InGaN/GaN MQWs have been successfully grown on V-grooved (001)Si substrate. The study on growth evolution reveals that the growth proceeds in two steps, namely heteroepitaxial growth and homoepitaxial growth, sequentially. No crack is found in both two growth stages, implying the low residual stress in the GaN epilayers grown by this technique. This is also confirmed by TEM, which shows that the lattice constant of the {1-101}GaN is very close to that of a fully-relaxed GaN substrate. Power-dependent photoluminescence measurements reveal that {1-101}InGaN/GaN MQW exhibits less wavelength shift than its (0001) counterpart, implying that the internal electric field of semi-polar {1-101}InGaN/GaN MQW is reduced. This is consistent with the results of time-resolved photoluminescence measurements, which show that the PL decay time is significantly shorter for the {1-101}InGaN/GaN MQW (0.44 ns) than the (0001)InGaN/GaN MQW (9.87 ns). Enhanced luminescence efficiency is observed on the {1-101}InGaN/GaN MQW as well. This approach is considered very promising for producing high performance {1-101}GaN-based optical devices on (001)Si. In summary, selective epitaxial growth techniques of GaN on sapphire and microscale patterned Si substrate have been developed and demonstrated in this study. The GaN films grown by these techniques have low dislocation density and residual stress, which manifest their potential in yielding high quality III-nitride semiconductors and devices.