长波量子阱红外探测器的不同光栅耦合机制研究

The Study of Different Grating Coupling Based on Long Wavelength Quantum Well Infrared Photodetector Focal Plane

摘要: 量子阱红外光电探测器(QWIP)中的材料由各向异性材料组成，QWIP中的光吸收对应于QWIP子带之间的跳跃。由于n型QWIP材料(如GaAs)中导带Γ能谷电子的有效质量是各向同性的，因此器件无法吸收垂直于表面的入射光。为了吸收入射光，需要设计特殊的衍射耦合结构。为了比较不同衍射耦合对光响应的影响，在320 × 256规模QWIP焦平面阵列上设计了160 × 256个凹光栅和160 × 256个凸光栅的新结构。采用有限差分时域(FDTD)算法对两个光栅进行仿真，并计算出两个光栅的光响应。得到了不同偏置下QWIP凹面光栅耦合的焦平面阵列和凸光栅耦合的焦平面阵列的噪声、NETD和平均响应度等性能参数。结论是凸光栅焦平面阵列的响应大于相同背景水平下凹光栅焦平面阵列的响应。凸光栅焦平面阵列的平均响应度为20.99 mV/K，凹光栅焦平面阵列的平均响应度为10.1 mV/K。凹光栅焦平面阵列的非盲元率为99.4%，凸光栅焦平面阵列的非盲元率为99.5%。

Abstract: The materials in a quantum well infrared photodetector (QWIP) are composed of heterogeneous materials and the light absorption in a QWIP corresponds to a jump between the sub-bands of the QWIP. Since the effective mass of the conduction band Γ-energy valley electrons in n-type QWIP materials such as GaAs is isotropic, the devices are unable to absorb incident light perpendicular to the surface. In order to absorb the incident light, special diffraction coupling structures need to be designed. In this paper, in order to compare the effect of different diffraction coupling on the light response, a new structure consisting of 160 × 256 concave gratings and 160 × 256 convex gratings has been designed on a 320 × 256 scale QWIP focal plane array. The two gratings are simulated by finite difference time domain (FDTD) algorithm, and the light response of the two gratings is calculated. The performance parameters such as noise, NETD and average responsivity of QWIP coupled with concave gratings and convex gratings at different bias are obtained. The conclusion is that the response of the convex gratings focal plane array is greater than the response of the concave gratings focal plane array for the same background level. The average responsivity of the convex gratings focal plane array is 14.2 mV/K, and the average responsivity of the concave gratings focal plane array is 10.1 mV/K. The operable pixel factor of the concave gratings focal plane array is 99.3%, the operable pixel factor of the convex gratings focal plane array is 99.5%.