Study on small spacing total internal reflection quantum well infrared focal plane array device

Abstract

Since infrared detection was proposed, infrared detectors have been to the 3rd generation . Both of the small size and large scale are the requirements for the development of infrared detectors. At present, the focal plane array devices on the market have a relatively high difference between the response wavelength and the size of pixel and therefore, when dealing with long wavelength detection, there will be a large size FPA. The quantum well infrared focal plane array devices fabricated by GaAs/AlGaAs have been widely used due to high uniformity and mature technology, but in the field of long-wave and very-long-wave detection, if the traditional grating coupling structure is used, because the wavelength and the size of the pixel are close, a strong diffraction effect will occur before the infrared radiation reaches the active region. This will lead to significant crosstalk and errors. Therefore, using grating diffraction as the quantum well coupling mechanism limits the size of the pixel and as a coupling mechanism, it is difficult to achieve due to small pixel size. Therefore, this paper adopts the total internal reflection type coupling structure proposed by K.K.Choi, and compare it with the traditional grating coupling structure to study how this structure improves the performance when detecting long-wavelength and reducing the size of pixels. In this paper, a quantum well infrared focal plane array with a pixel size of 640×512, a center-to-center distance of 15 μm and a response wavelength of 10.55 μm is fabricated by using GaAs/AlGaAs and melting photoresist technology which is different with the method proposed by K.K.Choi to fabricate this structure. The FDTD-based open source field simulation software MEEP is used to simulate the field distribution of the devices and evaluate its performance about fighting against optical crosstalk of this structure and compare its performance with the grating coupling structure. In this paper, we also use MEEP to explore the influence of the reflection angle, the position of the active region, and the period of the quantum well on the distribution of the field inside the device, and calculate the electromagnetic wave’s energy of the active region as the evaluation factor. These results shows that these geometrical factors restrict each other, therefore, to produce a good QWIP FPA based on the total internal reflective structure, one need to take these factors into account to tune these parameters to maximize the optimized performance. The main content of the research is to fabricate a 640×512 total internal reflection quantum well infrared focal plane array device, and use the MEEP to study the electrical field distribution inside the device with related geometric factors.