28 April 2017 Effect of different buffer-layers on near-infrared response of GaAs photocathodes
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In view that enhancing near-infrared response of photocathodes is critical to the detection performance, we propose two technical approaches by changing the structure of buffer-layer underneath the active-layer, wherein one is to produce a graded band gap using the graded-composition structure, and the other is to produce a distributed Bragg reflector using the AlAs/GaAs supperlattice structure. Three types of reflection-mode GaAs photocathode samples grown by molecular beam epitaxy were prepared under the same condition. By comparison of activation photocurrent and spectral response among the three different samples, it is found that compared with the conventional sample, the samples with graded-composition and distributed Bragg reflector can obtain higher photocurrent and better response. The measured results of spectral response indicate that the samples without a distributed Bragg reflector exhibit a typical smooth spectral behavior, while the spectral response of the sample with a distributed Bragg reflector structure has a different resonance feature. The sample with the distributed Bragg reflector structure can obtain higher response than those without distributed Bragg reflector at some near-infrared wavelength positions. The peak positions of spectral response curve agree quite well with the dip positions in the reflectivity spectrum. This agreement demonstrates that the response enhancements are ascribed to the resonant absorption effect.
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Yijun Zhang, Yijun Zhang, Cheng Feng, Cheng Feng, Feng Shi, Feng Shi, Xiaohui Wang, Xiaohui Wang, Xinxin Liu, Xinxin Liu, Xiang Zhang, Xiang Zhang, Yunsheng Qian, Yunsheng Qian, } "Effect of different buffer-layers on near-infrared response of GaAs photocathodes", Proc. SPIE 10209, Image Sensing Technologies: Materials, Devices, Systems, and Applications IV, 1020918 (28 April 2017); doi: 10.1117/12.2261658; https://doi.org/10.1117/12.2261658

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