InSb Photodiodes with AlInSb Passivation for Noise Reduction
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Solution Overview
Problem
Conventional manufacturing processes for InSb-based infrared photodiodes and sensor arrays introduce surface defects, leading to high surface recombination velocity, increased dark current, and noise equivalent power, necessitating cryogenic cooling to partially recover sensitivity, which is costly and maintenance-intensive.
Innovation Solution
Forming a passivation layer from a wide bandgap material like AlInSb on the InSb substrate before creating photodiode detector regions, allowing P+ species implantation through this layer to form P+ regions, thereby reducing substrate defects and improving noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacturing processes are used to create photodiode detector regions, then detector functionality is achieved, but surface defects are introduced leading to high surface recombination velocity and increased dark current
Solution Approach 1:
A passivation layer is formed on the InSb substrate surface before creating the photodiode detector regions. This preliminary passivation action protects the substrate from damage during subsequent manufacturing processes, preventing surface defects from forming in the first place rather than attempting to repair them later.
Solution Approach 2:
The passivation layer acts as an intermediary protective barrier between the manufacturing processes and the InSb substrate. This intermediate layer prevents direct contact between harsh manufacturing conditions and the sensitive substrate surface, thereby reducing surface recombination velocity and dark current while allowing detector functionality to be achieved.
2Reliability
If cryogenic cooling is applied to recover sensitivity, then noise performance improves, but operational cost and maintenance complexity increase
Solution Approach 1:
The invention converts the harmful effect of surface defects into a benefit by applying passivation. The passivation layer transforms the problematic substrate surface into a protected, low-recombination surface, thereby improving noise performance and sensitivity without requiring cryogenic cooling systems.
Solution Approach 2:
Instead of implementing expensive, complex, and maintenance-intensive cryogenic cooling systems, the invention uses a simple, inexpensive passivation layer that provides the necessary noise performance improvement. The passivation layer is a cost-effective alternative that eliminates the need for costly cooling infrastructure.
3Object-generated harmful factors
If passivation layer is formed before detector region creation, then surface defects are reduced, but additional manufacturing steps are required
Solution Approach 1:
The passivation layer formation is merged with the detector region creation process. The passivation layer is formed first, then detector regions are created through implantation or epitaxial growth that integrates with the existing passivation structure, combining protection and functionality in a unified manufacturing approach.
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 results in fewer substrate defects, enhancing the noise performance of sensor arrays and reducing the need for cryogenic cooling, thereby improving sensitivity and operational efficiency.
Implementation Method 1
high surface recombination velocity
Implementation Method 2
selectively implanting P+ species through the passivation layer to form P+ regions
Implementation Method 3
InSb-based photodiode detectors are used in many infrared sensor applications
Data Source
AI summary
InSb infrared photodiodes and sensor arrays with improved passivation layers and methods for making same are disclosed. In the method, a passivation layer of AlInSb is deposited on an n-type InSb substrate using molecular beam epitaxy before photodiode detector regions are formed in the n-type substrate. Then, a suitable P+ dopant is implanted directly through the AlInSb passivation layer to form photodiode detector regions. Next, the AlInSb passivation layer is selectively removed, exposing first regions of the InSb substrate, and gate contacts are formed in the first regions of the InSb substrate. Then, additional portions of the AlInSb passivation layer are selectively removed above the photodiode detectors exposing second regions. Next, metal contacts are formed in the second regions, and bump contacts are formed atop the metal contacts. Then, an antireflection coating is applied to a side of the substrate opposite from the side having the metal and bump contacts. Forming the AlInSb passivation layer before the photodiode detector regions reduces the number of defects created in the n-type InSb substrate during fabrication in comparison to conventional methods and improves the noise performance of InSb photodiodes and sensor arrays incorporating the improved passivation layer.