As the technologies in focal plane array (FPA) progresses, the industry is pushing for smaller pixel size and spacing between the pixels. The reduction in pixel size and spacing will increase both the resolution and fill factor which reduces the cost and increases the performance. However, as the density of the array elements increases, the crosstalk between the nearest neighboring pixels become a significant issue. Here we examine the case for a planer FPA with epitaxially grown NIN⁺ structure and the planer junctions are formed by diffusing P-type dopant into the N doped layer. We first examine the possible spacing by considering the lateral depletion region width to set the upper boundary for the spacing. The depletion region width is calculated by solving Poisson’s equation for Gaussian doping profile and the isolation of adjacent pixel is dependent on the formation of the back to back diodes to block the current flowing towards the device. Therefore overlap of the depletion regions indicates shorting and sets the minimum possible spacing for this structure. The electrical and optical crosstalks are modeled by using a DC resistive model to gauge the effect of current flow as the spacing reduces. Series of device arrays with various device pitches and device sizes ranging from 5 μm to 10 μm with device pitch from 5.5 μm to 15 μm are fabricated and tested under both dark and illumination conditions for their electrical performances including the crosstalk. The simulated and measured results will be presented.

Date Published: 11 June 2014
PDF: 7 pages
Proc. SPIE 9100, Image Sensing Technologies: Materials, Devices, Systems, and Applications, 91000K (11 June 2014); doi: 10.1117/12.2058154

Published in SPIE Proceedings Vol. 9100:
Image Sensing Technologies: Materials, Devices, Systems, and Applications
Nibir K. Dhar; Achyut K. Dutta, Editor(s)