An Amplified Imaging Sensor using a-Si:H Supper-lattice Photoconductive Layer

实现比人类视觉具有更高灵敏度的固态成像传感器是我们面临的一个重要问题。为了满足这一需求，必须解决以下几个问题。a)孔径比为100%的器件结构。b)可以在像素中放大光激发载波的像素结构。c)实现量子效率大于单位的光电子转换新概念。这项研究的重要结果如下。1)实现了a-Si:H光电二极管层叠加的放大型固态成像仪，实现了孔径比100%。实验结果表明，所提出的器件结构可用于未来的高清成像仪。2)提出了一种新的雪崩倍增器件结构，获得了大于100的倍增增益。有效量子效率超过单位的固态成像仪的实现成为可能。3)提出了一种载流子倍增区和光子吸收区可相互分离的a-Si:H光电二极管层结构，并观察到雪崩倍增引起的电流放大。结果表明，采用a-Si_3N_4层的阻挡结构可以有效地防止电极的空穴注入。设计并制备了a-Si:H/a-SiC:H超晶格雪崩光电二极管层。验证了机组的高转换效率。4)制备了具有边缘几何形状的Spindt场电子发射，当外加电压在500V范围内时，每个尖端的发射电平高达40 muA。结果表明，该阴极的发射能级明显高于采用相同工艺制备的锥形阴极。边缘型发射阵列是适用于未来固态成像仪的最佳结构。

Realization of the solid-state imaging sensor having a superior sensitivity over the human vision is important problem for us. To satisfy the demand, following subjects must be solved. a) The device structure with the aperture ratio of 100%. b) Pixel structure which the photo-excited carrier can be amplified in the pixel. c) New photo-electron conversion concept by which quantum efficiency larger than unity can be realized. The important results from this study are following. 1) The amplified solid-state imager overlaid by a-Si:H photodiode layer was implemented and the aperture ratio of 100% was realized. It was shown that the proposed device structure is available to future high definition imager. 2) New device structure using an avalanche multiplication was proposed and the multiplication gain over 100 was obtained. The realization of the solid-state imager having the effective quantum efficiency exceeding unity became possible. 3) An a-Si:H photodiode layer structure, which two regions, the carrier multiplication and the photon absorption can be separated each other, was proposed and the current amplification due to the avalanche multiplication was observed. It was shown that the blocking structure using the a-Si_3N_4 layer is suitable to prevent the hole injection from the electrode. An a-Si:H/a-SiC:H supper-lattice avalanche photodiode layer was also designed and fabricated. High conversion efficiency over unity was confirmed. 4) Spindt field electron emissions with rim geometry was fabricated and the emission levels of up to 40 muA per tip with applied voltage in the 500V range. It was found that the emission levels were larger than that of cone geometry cathode made by same fabrication process. The rim type emission array is the optimum structure applicable to the future solid-state imager.