Low-loss amorphous silicon wire waveguide for integrated photonics: effect of fabrication process and the thermal stability.
Low-loss amorphous silicon wire waveguide for integrated photonics: effect of fabrication process and the thermal stability.
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DOI：
10.1364/oe.18.025283
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发表时间：
2010-11
期刊：
影响因子：
3.8
通讯作者：
Shiyang Zhu;G. Lo;Dim-Lee Kwong
中科院分区：
文献类型：
--
作者：
Shiyang Zhu;G. Lo;Dim-Lee Kwong
采用等离子体增强化学气相沉积和各向异性干法刻蚀技术制备了氢化非晶硅（a-Si：H）线波导。在优化的工艺条件下，采用标准缩减法测量了200 nm（高）× 500 nm（宽）线波导在1550 nm处TE模和TM模的传输损耗分别为3.2 ± 0.2 dB/cm和2.3 ± 0.1 dB/cm。损耗在较短波长处变大（在1520 nm处，TE为~4.4 dB/cm，TM为~5.0 dB/cm），在较长波长处变小（在1620 nm处，TE为~1.9 dB/cm，TM为~1.4 dB/cm）。随着波导宽度从500 nm缩小到300 nm，TM模损耗几乎保持不变，而TE模损耗增加，表明波导侧壁粗糙度是主要的损耗贡献者，与晶体硅波导相似。虽然a-Si：H和上包层SiO2都是在400°C下沉积的，但是所制造的a-Si：H线波导的传播损耗在大于300°C的温度下在大气下的炉退火时开始增加：在400°C/30分钟退火之后为〜 13-15 dB/cm，并且在500°C/30分钟退火之后为>70 dB/cm，这可以归因于氢向外扩散。甚至更高的温度（即，>600°C）退火导致传播损耗接近多晶硅对应物（~40-50 dB/cm），这是由于a-Si：H固相结晶的开始。
Hydrogenated amorphous silicon (a-Si:H) wire waveguides were fabricated by plasma-enhanced chemical vapor deposition and anisotropic dry etching. With the optimized fabrication process, the propagation losses of as low as 3.2 ± 0.2 dB/cm for the TE mode and 2.3 ± 0.1 dB/cm for the TM mode were measured for the 200 nm (height) × 500 nm (width) wire waveguides at 1550 nm using the standard cutback method. The loss becomes larger at shorter wavelength (~4.4 dB/cm for TE and ~5.0 dB/cm for TM at 1520 nm) and smaller at longer wavelength (~1.9 dB/cm for TE and ~1.4 dB/cm for TM at 1620 nm). With the waveguide width shrinking from 500 nm to 300 nm, the TM mode loss keeps almost unchanged whereas the TE mode loss increases, indicating that the predominant loss contributor is the waveguide sidewall roughness, similar to the crystalline silicon waveguides. Although the a-Si:H and the upper cladding SiO2 were both deposited at 400°C, the propagation loss of the fabricated a-Si:H wire waveguides starts to increase upon furnace annealing under atmosphere at a temperature larger than 300°C: ~13-15 dB/cm after 400°C/30 min annealing and >70 dB/cm after 500°C/30 min annealing, which can be attributed to hydrogen out-diffusion. Even higher temperature (i.e., >600°C) annealing leads to the propagation loss approaching to the polycrystalline silicon counterparts (~40-50 dB/cm) due to onset of a-Si:H solid-phase crystallization.