Ultra Low Dark Current PIN Photodetector Design
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Solution Overview
Problem
Current photodetectors face challenges in reducing dark current, particularly generation current due to defects in the material or at the surface, which dominates total dark current in small pixels used for imaging arrays at or below room temperature, despite efforts to reduce diffusion currents.
Innovation Solution
A photodetector design incorporating an N-doped interface layer between the intrinsic absorption layer and cap layer, along with a P+ diffusion region and dielectric passivation, is used to reduce depletion width and generation current, featuring a substrate, buffer, absorption, and cap layers with specific doping and material compositions to minimize dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple layers with different doping concentrations are implemented, then dark current is reduced, but device complexity increases
Solution Approach 1:
The absorption layer combines multiple functional regions into a single integrated structure. The first and second regions are merged within the same absorption layer, allowing the device to achieve reduced dark current from both diffusion and generation mechanisms without requiring completely separate layers or structures for each function.
Solution Approach 2:
The absorption layer serves multiple functions simultaneously: it absorbs photons to generate carriers, reduces diffusion current through its first doped region, and reduces generation current through its second doped region. This multi-functionality is achieved within a single layer structure, avoiding the need for multiple separate components.
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 design significantly reduces dark current density by a factor of nine and overall noise by three, maintaining responsivity and capacitance, enabling effective operation without thermo-electric cooling for applications like night vision cameras and astronomical imaging.
Implementation Method 1
an absorption layer formed on the buffer layer for receiving incident photons and generating charged carriers
Implementation Method 2
A P+ diffusion region may be formed within the cap layer, the N-doped interface layer and at least a portion of the absorption layer
Data Source
AI summary
A photodetector and a method for fabricating a photodetector. The photodetector may include a substrate, a buffer layer formed on the substrate, and an absorption layer formed on the buffer layer for receiving incident photons and generating charged carriers. An N-doped interface layer may be formed on the absorption layer, an N-doped cap layer may be formed on the N-doped interface layer, and a dielectric passivation layer may be formed above the cap layer. A P+ diffusion region may be formed within the cap layer, the N-doped interface layer and at least a portion of the absorption layer, and at least one contact may be formed on and coupled to the P+ diffusion region.