Characterization of the high power laser diode and beta iron disilicde by microscopic Raman spectroscopy

在这个项目中，我们已经调查了显微拉曼光谱的高功率激光二极管端面的表征的可用性，并已通过脉冲激光沉积方法沉积的二硅化铁的基本性质进行了表征。在工作状态下，对紫光激光二极管端面进行了显微拉曼光谱分析.有源半导体激光器发出的激光可以被滤光片阻挡，其能级低到足以获得拉曼信号。虽然适用于红色激光二极管，但由于二极管的强黄光发射，认为该方法不适用于GaN系统。即使在阈值电流下，这种强黄色发射也与相对弱的拉曼信号重叠。根据理论上的考虑，难以通过晶体的热传导去除在高功率操作条件下在发光器件的刻面处产生的热能。解决这一问题的直接方法是在器件封装中填充导热流体。采用室温脉冲激光沉积和350℃以下退火的方法，在低温下成功地形成了液滴状的β-FeSi_2多晶微结构。通过显微拉曼光谱和透射电子显微镜分析得到了β相形成的证据。低温性质可能源于中间非晶相的形成，该中间非晶相可能由从由激光烧蚀产生的Fe-Si熔体中的快速热移除提供。这种低温方案提供了一种无需高温工艺而制备多晶β-FeSi_2的替代方法，其可以有利地与标准Si器件制造工艺兼容。

In this project we have surveyed the availability of microscopic Raman spectroscopy for the characterization of the high power laser diode facet and have characterized the basic properties of iron disilicide deposited by pulsed laser deposition method.Most generally GaN and related alloys are used on blue or violet laser diodes. We applied the microscopic Raman spectroscopy to the violet laser diode facet in operating condition. Laser light from active laser diode can be blocked by the filter and its level is low enough to obtain Raman signal. Although applicable to the red laser diode, it is considered that this method is not applicable to GaN system because of the strong yellow emission from the diode. This strong yellow emission overlaps with relatively weak Raman signal, even under threshold current. According to the theoretical consideration, it is difficult to remove the thermal energy produced at the facets of the light emitting devices under high power operation condition by thermal conduction of the crystals. Direct solution of this problem is to fill the device package with the thermal conduction fluid. Helium is the most effective material and some liquids are available depending on the condition of devices.β-FeSi_2 polycrystalline microstructure was successfully formed at low temperature in the form of droplet with room temperature pursed laser deposition and post-annealing below 350℃ employed. Evidence of the β-phase formation was obtained through microscopic Raman spectroscopy and TEM analysis. The low temperature nature may originate from formation of intermediate amorphous phase possibly provided by quick heat removal from Fe-Si melts generated by laser ablation. This low temperature scheme offers an alternative method of producing polycrystalline β-FeSi_2 without higher temperature processes, which could be beneficially compatible with the standard Si device fabrication processes.