SP调制的底部光栅长波/甚长波双色QWIP研究

The bottom coupling grating structure (BCGS) is proposed based on the surface Plasmon(SP) due to low coupling efficiency of top grating in dual color QWIP FPA. The object for this research is to improve coupling efficiency of positive incident light and to realize the high coupling efficiency of Long-/very long-wavelength dual-color. Therefore, firstly, the 2D metal grating will be fabricated on GaAs substrate. Secondly, the dual-color active region will be growth on the metal-semiconductor periodic interface. At last the dual-color unit device and 16 ×16 small size array device will be made. The main contents should be included four aspects. Firstly the characteristic of optical field distribution under the SP effect and the optimization parameter design of dual-color bottom grating will be studied. Secondly, the long-/very long- dual color active region will be designed and fabricated. Thirdly, the investigation about main characteristic of the BCGS will be studied through the optimal fabrication process of large area, high uniform grating coupling layer.At last, the growth mechanism of active region on metal-semiconductor interface will be studied. Comparing with traditional top grating, theadvantages of BCGS are that the separation of coupling layer and the photosensitive element electrode will be realized, the problem of low coupling efficiency caused by photosensitive cell size reducing is solved and the QWIP photocurrent is also increased. The research will lay the foundation for the realization of high sensitivity, large size dual-color QWIP FPA through improving the main characteristic.

针对双色QWIPFPA顶部光栅耦合效率较低的问题，提出表面等离激元(SP)调制的底部光栅耦合层结构，实现长波/甚长波双色的同时高效率耦合。为此，拟首先在GaAs衬底上制备二维周期性金属光栅耦合层，然后在光栅表面生长长波/甚长波双色有源区，并实现双色单元器件及16×16小规格面阵的制备。主要研究内容包括：(1)SP效应对双色有源区内光场的调制机理及光栅参数的最优设计；(2)长波/甚长波双色叠层有源区的设计与实现；(3)高均匀性光栅结构的工艺实现；(4)金属-半导体周期性界面上有源区的生长机理。与传统顶部光栅相比，底部光栅实现了光栅耦合层与光敏元电极的分离，保持了光栅的完整，避免了光敏单元尺寸减小导致的光栅耦合效率降低；可望在降低面阵制备工艺复杂度的同时，大幅提高QWIP器件的光电流。项目研究有助于提高双色QWIP的探测率，为高灵敏度大规格双色QWIPFPA 的实现奠定基础。

本项目主要开展长波/甚长波双色量子阱红外探测器的研究，针对双色 QWIP FPA顶部光栅耦合效率较低的问题，采用表面等离激元调制的底部光栅耦合结构来实现长波/甚长波双色的同时耦合，主要研究内容如下：.1、光栅参数的优化。采用表面等离激元效应来提高量子阱红外探测器中二维光栅的耦合效率。利用三维时域有限差分算法，分析表面等离激元作用下，长波量子阱红外探测器中二维金属薄膜光栅参数对入射光的调制作用。结果表明，对于8微米的入射光，当光栅周期为2.8微米，孔直径为1.4um，光栅厚度为40nm时，X-Y平面内Z方向电厂值最大，光栅的耦合效率最高。.2、太赫兹量子阱探测器二维光栅耦合效率的分析。将二维金属光栅结构引入到探测器结构中，以提高太赫兹量子阱光电探测器的探测率。采用三维时域有限差分算法，建立了太赫兹量子阱光电探测器的二维金属光栅仿真模型，详细分析了二维金属光栅参数对太赫兹量子阱光电探测器的电场强度的影响。结果表明：当入射光频率为6.27THz、光栅周期 P=10.5 um、占空比=0.55（金属块宽度ｗ＝5.755um ）、光栅层厚度h=0.4um时，器件中的Z方向上的电场值最大，光栅的耦合效率最高。.3、高性能金属线栅型太赫兹偏振器的研究。采用半导体光刻工艺设计并制作了一种新型的宽带太赫兹偏振片，该偏振片采用双面双层金属光栅结构，其平均消光比在0.5和2.0THz可达到60dB，在1.06THz可达到87dB，该结构的消光比远远高于传统的单层线栅结构的偏振片。.4、表面量子点与掩埋量子点的光学特性研究。采用分子束外延方法，在同一GaAs衬底上分别生长了11摩尔的掩埋量子点和表面量子点层，两层量子点之间用70nm厚的GaAs材料隔开。采用光致发光的光谱测量方法仔细研究了两个量子点层的光学特性，仔细对比了两者的光致发光谱密度、线宽和寿命的不同特性及其随温度和激发光强的变化，证实并阐述了表面态对表面量子点的光学特性的影响以及载流子在表面态和表面量子点的束缚态之间的跃迁机制。