标题: 锑化镓基第一型砷锑化铟镓/砷锑化铝镓量子井之研究及在中红外线雷射之应用
GaSb-based Type-I InGaAsSb/AlGaAsSb Quantum Wells and Their Applications to Mid-Infrared Lasers
作者: 林建宏
Lin, Chien-Hung
李建平
Lee, Chien-Ping
电子工程学系 电子研究所
关键字: 砷锑化铟镓/砷锑化铝镓量子井;中红外线雷射;分子束磊晶;光激发萤光;双波长雷射;面射型光子晶体雷射;InGaAsSb/AlGaAsSb Quantum Wells;Mid-infrared Laser;Molecular Beam Epitaxy;Photoluminescence;Dual Wavelength Laser;Photonic Crystal Surface Emitting Laser
公开日期: 2015
摘要: 此论文主要致力于锑化镓基第一型砷锑化铟镓/砷锑化铝镓量子井之探讨,并且找寻出更好的长晶方法来提升其光学特性。我们更进一步地利用此锑化合物材料系统来开发于中红外线应用的发光元件。我们利用了分子束磊晶的技术来成长砷锑化铟镓/砷锑化铝镓四元量子井系统。透过介面处五族元素的控制,我们成长出高品质的量子井材料。在未优化的量子井界面处,时常存在着非理想的局部局限能阶,进而影响激子的复合机制。透过介面处五族元素的控制,我们获得了拥有优异光学性质的量子井样品,并且此样品极少受到局部局限能阶的影响。我们利用温度相依及激发强度相依的光激发萤光实验进行了广泛的量子井探讨。在室温下,我们观察到波长在2.2微米的高强度且高效率的激子发光。在低温下,萤光几乎保持不变的强度,并且极少受到局限能阶的消光作用。量子井随温度改变的发光能量变化类似于块材行为,此现象进一步说明了量子井与周围能障之间拥有优异的介面性质。因为此良好的介面性质,我们得到了此量子井系统本质的不均匀性线宽扩展只有极小的5 meV。
针对中红外线的应用,我们发展出两种型态的雷射元件。第一是中红外双波长雷射;第二是中红外面射型光子晶体雷射。
在单一波导的雷射结构中,我们在主动层成长了两种不同成分比例的砷锑化铟镓/砷锑化铝镓量子井,并且利用一载子局限层将此两种量子井隔开。利用光学注入的方式,我们成功地在室温下展现出中红外线双波长雷射输出的特性。雷射波长分别为2.31微米与2.61微米,波长差距达300奈米。我们也观察到在特定的共振腔长度下,两波长可同时达到阀值条件并且产生雷射输出。
最后我们成功实现了可高于室温操作的光激发面射型光子晶体雷射。在室温下,雷射发光波长在2.3微米,波长半高宽约0.3奈米;雷射的阀值密度约为0.3 kW/cm2。元件表面的正方晶格光子晶体结构提供了光学回馈以及光学耦合机制以达到面出光雷射输出。此元件可达到在350 K的高温下操作,随温度变化的雷射波长改变速率仅约0.21 nm/K。同时,我们也进行了不同光子晶体蚀刻深度的探讨与模拟研究。光场与光子晶体的耦合强度随着蚀刻深度加深而增加,进而使得雷射波长蓝移以及降低雷射阀值,理论模拟与实验结果可以得到良好的吻合。
In this dissertation we studied the growth and material properties of GaSb-based type-I InGaAsSb/AlGaAsSb quantum wells (QWs) and their applications to mid-infrared (mid-IR) opto-devices. We developed a molecular beam epitaxy (MBE) growth technique that could greatly improve the optical qualities of the QWs. By controlling the group-V elements at interfaces during growth, we were able to achieve high quality QWs free from undesired localized trap states, which might otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature (RT) with a wavelength of 2.2 m were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remained nearly constant at low temperatures and was free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening was as small as 5 meV.
Based on the high quality QWs obtained by the above mentioned technique, we developed two types of mid-IR laser devices in this Sb-based material system. One is a dual wavelength laser and the other is a photonic crystal surface emitting laser (PCSEL).
For the dual wavelength lasers, two kinds of InGaAsSb/AlGaAsSb QWs with different compositions were grown as the active region in a single waveguide laser structure. A proper barrier was added in the structure to isolate the two well sections. Two wavelength emissions at 2.31 m and 2.61 m were obtained at RT by optical pumping (the wavelength difference is up to 300 nm). When the cavity length is properly chosen, both wavelengths reach the threshold simultaneously.
Second, we demonstrated above RT optically pumped GaSb-based mid-IR PCSELs. The lasers emitted at a wavelength of ~ 2.3 m with a line width of 0.3 nm and a threshold power density of ~ 0.3 kW/cm2 at RT. The square lattice photonic crystal (PC) on the surface provides the optical feedback for laser operation and light coupling for surface emission. The PCSELs were operated with temperatures up to 350 K, showing a small wavelength shift rate of 0.21 nm/K. The PCSELs with different PC etching depth were studied and simulated. As optical field couples more into the PC region due to the increase of etching depth, both the lasing wavelength and the threshold power density decrease. The calculations could fit well with the experimental results.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079711813
http://hdl.handle.net/11536/126099
显示于类别:Thesis