Reduced Junction Area Barrier Photodetector
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Solution Overview
Problem
Infrared photodetectors with barrier layers between like-conductively doped semiconductor layers face issues with unwanted dark current due to the barrier layer, which affects device performance by generating recombination and surface currents.
Innovation Solution
A method involving selective etching to reduce the surface area of the barrier layer, leaving gaps with remaining sidewall portions, and filling these gaps with a filler material using atomic layer deposition to maintain absorption volume while reducing junction area and shunt currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier layer is used between like-conductively doped semiconductor layers to block majority carriers, then carrier blocking performance is improved, but dark current increases due to generation-recombination and surface current mechanisms
Solution Approach 1:
The barrier layer is segmented by selectively removing outer peripheral portions, dividing it into a central region and leaving gaps at the periphery. This segmentation reduces the total junction area where generation-recombination and surface currents occur, thereby reducing dark current while maintaining the carrier blocking function in the central region.
Solution Approach 2:
The harmful peripheral portions of the barrier layer are extracted or removed through selective etching. This removes the source of surface currents and reduces generation-recombination at the junction periphery, directly addressing the dark current problem while preserving the essential barrier function in the remaining central region.
2Object-generated harmful factors
If the barrier layer surface area is reduced to mitigate generation-recombination and surface currents, then dark current is reduced, but the absorption volume may be compromised
Solution Approach 1:
Different regions of the barrier layer are given different qualities: the central region maintains its full barrier properties for carrier blocking, while the peripheral regions are selectively removed to reduce surface currents. This local differentiation allows the structure to simultaneously achieve reduced dark current and maintained absorption volume.
Solution Approach 2:
The solution moves from a two-dimensional area reduction approach to a three-dimensional structure by creating gaps and filling them with filler material. This maintains the vertical absorption path length while reducing the horizontal junction area, effectively decoupling absorption volume from junction area.
3Object-generated harmful factors
If selective etching is used to remove outer peripheral portions of the barrier layer, then junction area is reduced and dark current is mitigated, but fabrication complexity increases
Solution Approach 1:
A filler material is introduced as an intermediary substance to fill the gaps created by selective etching. This filler material serves multiple functions: it maintains the pixel structure integrity, prevents collapse of the etched regions, and can provide additional passivation. The use of atomic layer deposition as the filling method provides precise control and conformal coverage, managing the fabrication complexity through a well-established process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach mitigates generation-recombination and surface current mechanisms, negates shunt currents, and maintains pixel integrity, enhancing device performance without altering existing design or fabrication processes.
Implementation Method 1
The selectively removing comprises exposing the structure to a selective etch, such selective etch selectively removing the outer peripheral portions of the barrier layer while leaving unetched the outer peripheral portions of the upper and lower layers
Implementation Method 2
the filling comprises using atomic layer deposition
Implementation Method 3
the barrier layer prevents the flow of majority carriers
Implementation Method 4
In response to infrared radiation, minority carriers, holes, pass between the upper and lower layers and through the barrier layer
Data Source
AI summary
A photodetector structure having a barrier layer disposed between a pair of like-conductively doped semiconductor layers, the barriers layer having a surface area smaller than the surface area of the upper one of the pair of semiconductor layers. A fill material is disposed between outer peripheral edges of the barrier layer and a region between outer peripheral edges of the first and second layers.