High temperature annealing of rare earth implanted GaN films: Structural and optical properties
High temperature annealing of rare earth implanted GaN films: Structural and optical properties
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DOI：
10.1016/j.optmat.2005.09.015
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发表时间：
2006-05
影响因子：
3.9
通讯作者：
K. Lorenz;U. Wahl;E. Alves;E. Nogales;S. Dalmasso;R. Martin;K. O'Donnell;M. Wojdak;A. Braud;T. Monteiro;T. Wojtowicz;P. Ruterana;S. Ruffenach;O. Briot
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文献类型：
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作者：
K. Lorenz;U. Wahl;E. Alves;E. Nogales;S. Dalmasso;R. Martin;K. O'Donnell;M. Wojdak;A. Braud;T. Monteiro;T. Wojtowicz;P. Ruterana;S. Ruffenach;O. Briot
在MOCVD生长的GaN外延层上进行了不同注入条件下的Tm和Eu离子注入，以优化注入参数：注量、注入温度和能量。利用沟道模式下的卢瑟福背散射光谱（RBS/C）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、变温光致发光（PL）和室温阴极发光（CL）研究了样品的结构和光学性质。比较了不同的退火方法。根据RBS/C测量，Tm在低能量密度被发现完全纳入替代Ga-网站，而对于更高的能量密度的替代分数减少。增加的能量密度导致增加的损伤水平，并最终形成部分非晶，纳米晶表面层。发光强度随注量的增加先增大后减小。然而，当能量密度超过2× 1015 Tm/cm 2时，它又下降了，表明结构和光学性质之间有很强的相关性。在较高的温度下注入抑制了纳米晶层的形成，并增加了替代分数和发光强度。我们还发现，薄的AlN帽的存在下，保护样品在植入后的高温退火，并防止形成纳米晶表面层在植入过程中，即使对于高通量。在1000 - 1300°C的退火温度范围内，室温下622 nm附近的Eu相关发光强度增加了40倍。
GaN epilayers grown by MOCVD were implanted with Tm and Eu under different implantation conditions, in order to optimize the implantation parameters of fluence, implantation temperature and energy. Rutherford backscattering spectrometry in the channelling mode (RBS/C), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-dependent photoluminescence (PL) and room temperature cathodoluminescence (CL) were used to study structural and optical properties of the samples. Different annealing methods are compared. According to RBS/C measurements, Tm at low fluences is found to incorporate entirely on substitutional Ga-sites while for higher fluences the substitutional fraction decreases. Increasing the fluence leads to increasing damage levels and finally to the formation of a partially amorphous, nanocrystalline surface layer. The luminescence intensity increases with fluence at first. However, for fluences in excess of 2×1015Tm/cm2it decreases again, showing a strong correlation between structural and optical properties. Implanting at higher temperature inhibits the formation of the nanocrystalline layer and increases both the substitutional fraction and the luminescence intensity. We also found that the presence of a thin AlN cap protects the sample during post-implant high temperature annealing and prevents the formation of a nanocrystalline surface layer during the implantation even for high fluences. The intensity of Eu-related CL near 622nm at room temperature increases by a factor of 40 within the studied annealing range from 1000 to 1300°C.