The shortwave infrared band(SWIR) of 0.9 ~ 1.7 $\mum$ has been fascinating because of its particular spectroscopic characteristics such as the ambient night glow and the penetration of dust and smog. The SWIR detectors based on InGaAs/InP PIN photodiode arrays are widely used in various applications such as surveillance and reconnaissance systems due to its advantages of the low dark current characteristics and the high quantum efficiency. Among these figure of merits for SWIR photodiode arrays, the crosstalk characteristics are an important performance parameter of the SWIR detectors because it has an effect on the imaging quality. However, as the pixel size shrinks, the crosstalk effects cause the more serious problems in the imaging resolution of the pixel arrays. Generally the crosstalk of neighboring pixels includes the electric and optical components. The electrical crosstalk is mainly caused by the lateral diffusion of carriers and the optical crosstalk is caused by the optical proper-ties such as reflection, refraction and diffraction.
In this thesis, the conventional planar-type InGaAs/InP PIN photodiodes have been successfully characterized by using a new measurement setup. To measure the crosstalk characteristics accurately, it is necessary that the diameter of spot size be smaller than dimension of detectors. In the new measurement system, it is verified that the laser beam spot size of 9.56 $\mum$ using a laser beam profiler and a resolution step of 10 $\mum$ in the measurement setup. At a pixel pitch of 200 $\mum$ with an active area of 100 $\mum$, the crosstalk characteristics of a nearest-neighbor pixel and next nearest-neighbor pixel are 7.81 % and 1.71 %, respectively. As the pixel size is smaller, it is presented that the crosstalk characteristics of a neighbor and next-neighbor pixel are abruptly increased. In order to analysis of the crosstalk characteristics, the crosstalk numerical model is used for analyzing the dominant components of the crosstalk characteristics. As a results, the electrical crosstalk components is 67.7 times larger than that of the optical crosstalk components.
Next, to improve the crosstalk characteristics, an electrical crosstalk sup-pressing structure with deep guard-ring is proposed and characterized. To form deep guard-ring using Zn Spin-on-Glass (Zn-SOG) technique, the etching technique is used to reduce the complicated double diffusion sequences to a single process step. In order to obtain the optimal guard-ring bias conditions, various bias conditions are applied in guard-ring contacts. From measurement results, the optimum guard-ring bias is 0 V in this work. At pixel pitch of 200 $\mum$, the fabricated planar-type PIN photodiode arrays with guard-ring show a crosstalk characteristic of 2.57 % which is the best value in this work. The crosstalk characteristics of the fabricated planar-type PIN photodiodes at 150 $\mum$ pixel pitch measured to be 2.19 % which is about 9 times lower than that of conventional planar-type PIN photodiodes.
Consequently, the planar-type InGaAs/InP PIN photodiodes with guard-ring electrodes are very promising candidates for SWIR imaging applications.
SWIR 대역 영상 시스템의 응용을 위해, 낮은 crosstalk 특성을 가지는 평면형 InGaAs/InP PIN photodiode의 설계하고 제작하였다.
다양한 장점을 지닌 평면형 SWIR photodiode는 많은 연구 및 개발이 진행되었다. 이러한 장점 중 crosstalk 특성을 개선시키기 위해 기존에 사용되었던 구조를 제작 및 측정하였다. 이를 위해 먼저 측정 셋업을 진행하였으며 그 결과 9.56 μm의 laser beam spot을 가지는 측정 셋업을 구현하였고, 이를 통해 기존 소자의 crosstalk을 분석하였다. 이를 통해 기존 구조의 crosstalk 특성이 200 $\mum$의 pixel pitch를 가지는 소자의 경우 nearest-neighbor pixel 기준 7.81 %로 측정 되었다. 또한 기존에 제시되었던 모델링을 이용하여 광 전류를 분석한 결과 electrical crosstalk 성분이 optical crosstalk 성분보다 67.7배 높은 성분을 가지고 있는 것을 확인하였다.
이를 토대로 crosstalk 특성을 향상시킬 수 있는 구조를 제안하였다. 이를 통해 기존 구조 대비 향상된 crosstalk 효과를 확인하였다. Deep guard-ring에서의 0 V 바이어스에서 2.57 % 낮은 crosstalk 특성을 얻을 수 있었으며 이를 모델링을 통해 분석한 결과, effective diffusion length의 감소로 인해 crosstalk이 향상되었다는 사실을 알 수 있었다. 측정 결과를 종합하여 볼 때 deep guard-ring 구조가 더 작은 pixel pitch를 가지는 소자에서 효과를 보일 것으로 예상되며, SWIR imaging system 응용분야에서 가능성이 높은 구조라 볼 수 있다.
