Characteristics of Metallic Grating on Quantum Well Infrared Photodetector
Date Issued
2007
Date
2007
Author(s)
Lai, Ching-Hung
DOI
zh-TW
Abstract
Electromagnetic wave exited around metallic grating and transmitted through grating is complicated and interesting. Recent studies about subwavelength metallic structure were mainly experiments measuring transmission spectrums which photodectors were set vary far from the sample. We wanted to understand the characteristics of grating near the sample. We fabricated grating structure on QWIP and the active region of QWIP is under the surface about 1 μm. By observing spectral response of QWIP with grating, we successively found fundamental characteristics about grating and there was a good correspondence to transmission spectrums.
The experiments showed that the grating peak appeared at similar position in response of QWIP and transmission spectrum of sample, dominated by period of grating and refractive index of substrate. The grating peak of QWIP experiment was excited by TM incident light, but TE incident contributed peak in transmission spectrum, due to the distance of the measurement. We tuned the grating peak to structure peak to enhance the responsivity. In the mean time, we discovered that the edge coupling provided a large part of response, which came from TM incident light in Brewster’s angle. Normal incidence of hollow frame also provided response because of finite size effect.
We discovered that the grating thickness could raise the ratio of TM over TE mode, because the TE mode decayed faster than TM mode. But it is a trade off that the total responsivity was decreased. At last, we could embed grating in to QWIP, the grating was much closer to the active region of QWIP. More quantity of exited wave absorbed to enhance responsivity. On the other hand, as the thickness increase, the transmitted electromagnetic wave decays, less wave went through grating to decrease responsivity. We could find some balance between these two factors.
Subjects
金屬光柵
QWIP(量子井紅外線光偵測器)
TE和TM模態
Brewster角
尺寸效應
metallic grating
QWIP
TE and TM mode
finite size effect
Type
thesis
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