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

在这个项目中，我们调查了微观拉曼光谱表征高功率激光二极管表面的可用性，并表征了脉冲激光沉积法沉积的二硅化铁的基本性质。一般来说，氮化镓和相关合金用于蓝色或紫色激光二极管。将显微拉曼光谱应用于工作状态下的紫色激光二极管表面。来自有源激光二极管的激光可以被滤光器阻挡，并且其电平足够低以获得拉曼信号。虽然该方法适用于红色激光二极管，但由于二极管发出强烈的黄色辐射，因此认为该方法不适用于GaN系统。这种强烈的黄色辐射与相对较弱的拉曼信号重叠，即使在阈值电流下也是如此。从理论上考虑，在高功率工作条件下，很难通过晶体的热传导去除发光器件表面产生的热能。直接解决这一问题的方法是在器件封装中填充导热流体。氦是最有效的材料，根据设备的条件，有些液体是可用的。采用室温脉冲激光沉积和350℃以下的后退火工艺，在低温条件下以液滴形式成功地形成了β-FeSi_2多晶微观结构。通过显微拉曼光谱和透射电镜分析获得了β相形成的证据。低温性质可能源于激光烧蚀产生的铁硅熔体快速脱热所提供的中间非晶相的形成。该低温方案为制备多晶β-FeSi_2提供了一种无需高温工艺的替代方法，可以与标准的Si器件制造工艺有利地兼容。

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.