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

在这个项目中，我们考察了显微拉曼光谱用于高功率激光二极管刻面表征的可行性，并表征了脉冲激光沉积方法沉积的二硅化铁的基本性质。通常情况下，GaN和相关合金用于蓝色或紫色激光二极管。在工作条件下，我们对紫外光激光二极管小面进行了显微拉曼光谱的测量。该滤光片可以阻挡来自有源激光二极管的激光，其能级足够低，可以获得拉曼信号。虽然这种方法适用于红光激光二极管，但由于二极管的强黄光发射，认为这种方法不适用于GaN系统。即使在阈值电流下，这种强烈的黄色发射也与相对较弱的拉曼信号重叠。根据理论考虑，在高功率工作条件下，发光器件端面产生的热能很难通过晶体的导热来消除。这个问题的直接解决方案是在器件封装中填充导热流体。氦是最有效的材料，根据器件条件的不同，也有一些液体可供选择。采用室温脉冲激光沉积和低于350℃的后退火，在低温下成功地形成了液滴状的多晶组织。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。低温性质可能源于激光烧蚀产生的Fe-Si熔体快速散热所形成的中间非晶相。这种低温方案提供了一种不需要高温工艺就可以制备多晶β-FeSi2的替代方法，它可以与标准的硅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.