Showing papers by "S.E. Holland published in 2014"
TL;DR: In this article, the authors present simple physics-based models for two effects that have been noted in the fully depleted CCDs that are presently used in the Dark Energy Survey Camera.
Abstract: In this work we present simple, physics-based models for two effects that have been noted in the fully depleted CCDs that are presently used in the Dark Energy Survey Camera. The first effect is the observation that the point-spread function increases slightly with the signal level. This is explained by considering the effect on charge-carrier diffusion due to the reduction in the magnitude of the channel potential as collected signal charge acts to partially neutralize the fixed charge in the depleted channel. The resulting reduced voltage drop across the carrier drift region decreases the vertical electric field and increases the carrier transit time. The second effect is the observation of low-level, concentric ring patterns seen in uniformly illuminated images. This effect is shown to be most likely due to lateral deflection of charge during the transit of the photo-generated carriers to the potential wells as a result of lateral electric fields. The lateral fields are a result of space charge in the fully depleted substrates arising from resistivity variations inherent to the growth of the high-resistivity silicon used to fabricate the CCDs.
28 citations
TL;DR: Efforts to reduce the read noise in fully depleted, scientific charge-coupled devices (CCDs) by implementing a direct contact between the output transistor, polysilicon-gate electrode and the floating diffusion.
Abstract: In this work we describe efforts to reduce the read noise in fully depleted, scientific charge-coupled devices (CCDs). The read noise is proportional to the total capacitance at the floating-diffusion node. Reductions in the capacitance at the floating diffusion are accomplished by implementing a direct contact between the output transistor, polysilicon-gate electrode and the floating diffusion. We have previously reported promising results for this technology that were measured on small-format CCDs with 4-channel readout where each channel had a different output transistor geometry. In this work we present the results of the use of this technology on 12 and 16-channel, large-format CCDs in order to determine the reproducibility of the process. The contact size for this work is two microns by two microns, and projection lithography was used to print the contacts. We have also utilized selective wafer-stepper lithography to generate contacts that are one micron on a side. We also describe efforts in the device design of the output transistor to further reduce the noise.
5 citations
TL;DR: In this paper, the authors present simple physics-based models for two effects that have been noted in the fully depleted CCDs that are presently used in the Dark Energy Survey Camera.
Abstract: In this work we present simple, physics-based models for two effects that have been noted in the fully depleted CCDs that are presently used in the Dark Energy Survey Camera. The first effect is the observation that the point-spread function increases slightly with the signal level. This is explained by considering the effect on charge-carrier diffusion due to the reduction in the magnitude of the channel potential as collected signal charge acts to partially neutralize the fixed charge in the depleted channel. The resulting reduced voltage drop across the carrier drift region decreases the vertical electric field and increases the carrier transit time. The second effect is the observation of low-level, concentric ring patterns seen in uniformly illuminated images. This effect is shown to be most likely due to lateral deflection of charge during the transit of the photogenerated carriers to the potential wells as a result of lateral electric fields. The lateral fields are a result of space charge in the fully depleted substrates arising from resistivity variations inherent to the growth of the high-resistivity silicon used to fabricate the CCDs.
4 citations