The Effect of Inter-Pixel Nested Ridges Incorporated in a stacked Gradient Homojunction Photodiode Architecture
Faculty of Computing, Health and Science
School of Engineering / Centre for Communications Engineering Research
The response resolution of the stacked gradient homojunction vertical single junction photodiode can be improved further by including a laterally stacked gradient homojunction in the form of inter-pixel nested ridges that extend from each epilayer towards the frontwall of the photodiode (Fig 4). In this study, we have simulated the effect of inter-pixel ridge height and width on the response resolution of a two dimensional CMOS compatible stacked gradient homojunction photodiode array. The results demonstrate enhanced relative crosstalk suppression and slightly enhanced maximum quantum efficiency compared to all photodiodes previously simulated by the authors, except for the double junction photodiode which demonstrated better crosstalk suppression though being much reduced in sensitivity. As inter-pixel nesting of ridges increases with increase in ridge height, the relative crosstalk reduces and the maximum quantum efficiency is improved to a constant level above that of the conventional stacked gradient homojunction photodiode. As the lateral gap between nested ridges increases and the ridges' widths reduce more rapidly through the underlying epilayers, the relative crosstalk deceases while the maximum quantum efficiency remains constant. Frontwall illumination is advantaged in reduced crosstalk due to the immediacy of illumination to the depletion region and being far from the substrate. Backwall illumination is superior in sensitivity due to more carriers being photogenerated outside the well and being focused into the depletion region by the two minority carrier mirrors.