CCD的近红外敏化技术

理论上硅ＣＣＤ在０ ．１ｎｍ 到１．１μｍ 之间都有响应， 但通常此种器件在８００ｎｍ 以后量子效率下降明显， 一般会小于５０ ％ 。其中最主要的原因是近红外光子的吸收深度大于ＣＣＤ 的外延层厚度， 使大量光子穿透整个器件。显然增加外延层的厚度是解决这一问题的良好途径。但随着外延层的增加， 必须使用高阻抗的材料， 否则会明显的减低分辨率。另外增透膜的使用也会使量子效率大幅度提高， 而且有效的减弱了干涉条纹的影响。新型Ｐ沟道Ｎ 衬底全耗尽高阻ＣＣＤ的出现， 使得量子效率在１μｍ 仍然接近６０％ 。

Silicon CCD Optimized for NIR Wavelengths

CCDs processed on typical substrates exhibit low NIR QE. Because the relatively thin epitaxial layer allows a high percentage of long wavelength photons to pass through and the reflection loss of back surface is high. A thick epitaxial layer allows the longer wavelength photons to bo absorbed into the epitaxial layer where the resultant electrons generated will be collected in the potential wells.The drawback of processing with this method is a resultant degradation of carrier diffusion MTF.Increasing the depleted region under each gate,which can be realized by using high resistivity substrates,can enhance MTF.A new kind of CCD fabricated on high resistivity silicon at Lick Observatory has superior red performance beyond 800 nm wavelength. The application of thin film AR coating directly on to the CCD back surface can significantly reduce reflection loss from UV to NIR and greatly decrease interference fringing on back illuminated CCDs.